On Variational Dynamics in Redshift Space

a r X i v :a s t r o -p h /9803259v 1 22 M a r 1998

Draft version February 1,2008

Preprint typeset using L A T E X style emulateapj

ON VARIATIONAL DYNAMICS IN REDSHIFT SPACE

Inga M.Schmoldt and Prasenjit Saha

Department of Physics (Astrophysics),Oxford University,Keble Road,Oxford OX13RH,UK

Draft version February 1,2008

ABSTRACT

Peebles (1989)showed that in the gravitational instability picture galaxy orbits can be traced back in time from a knowledge of their current positions,via a variational principle.We modify this variational principle so that galaxy redshifts can be input instead of distances,thereby recovering the distances.As a test problem,we apply the new method to a Local Group model.We infer M =4to 8×1012M ⊙depending on cosmology,implying that the dynamics of the outlying Local Group dwarves are consistent with the timing argument.Some algorithmic issues need to be addressed before the method can be applied to recover nonlinear evolution from large redshift surveys,but there are no more di?culties in principle.

Subject headings:large-scale structure of universe –galaxies:distances and redshifts –Local Group

1.INTRODUCTION

Phase space is six–dimensional and therefore six num-bers for each particle will specify the dynamics completely.The standard approach is to de?ne initial conditions as six numbers (positions and velocities in three dimensions)and integrate those forward in time.This is the usual N -body approach to the problem.

Alternatively,it is not necessary to de?ne those six num-bers at only one time.It is equally well possible to split them,such that three numbers will be known at an initial time,and three at a ?nal time,where the former are de-rived from physical arguments about the inital state,and the latter are provided by data on the current state of the system.This is the boundary value approach.

The usual boundary value for structure formation by hierarchical clustering at initial times is the gravitational instability requirement that initial peculiar velocities must vanish:therefore,it is possible to express the orbits as a sum of growing modes.This is what perturbation the-ory is designed to do,and linear perturbation theory and its extension,the Zel’dovich approximation are in wide use.However,as structure formation is non-linear on small scales,a non-linear formalism would be more useful.Non-linear perturbation theory exists (e.g.Nusser and Dekel (1993),Gramann (1993a),Gramann (1993b),Buchert and Ehlers (1993))but is very complicated and has conver-gence problems,i.e.the dynamics at early times can be ?tted to a high accuracy only at the expense of a good ?t at later times.

A di?erent method (cf Peebles (1989))of addressing the boundary value problem is to use the variational princi-ple.The basic method is to start with a parameterisation of the orbits which satis?es the boundary conditions and then adjust the parameters until a stationary point of the action is found.(A variant,suggested by Giavalisco et al.1993and implemented by Susperregi and Binney (1994),parameterises the density and velocity ?elds rather than the orbits.)This may seem like perturbation theory be-cause it is a method which attempts to get better and better approximations of galaxy orbits but there are im-portant di?erences.The main one is that perturbation

theory attempts to ?t early times even at the expense of accuracy at later times,whereas the variational principle spreads out the errors more uniformly over all times.The variational principle is also algorithmically more straight-forward to do to higher orders.

The main disadvantage of Peebles’original method is that it requires the input of distances to recover red-shifts.Redshifts,however,are easy to measure,whereas distances are not.We therefore change to recovering dis-tances from redshifts.The recent nearly all-sky redshift surveys QDOT and PSC z provide a strong motivation for variational methods in redshift space.Shaya,Peebles,and Tully (1993)and Shaya,Peebles,and Tully (1995)have pointed out that this could be achieved by treating the distance boundary condition as a parameter and ?tting that until the recovered redshifts agree with the measured ones.Another approach is to modify the variational prin-ciple until the boundary conditions are of the desired form.We take such an approach and so does Whiting (1998)but the details in his treatment di?er from ours.The attrac-tive feature of this approach is that it only requires small modi?cations of Peebles’elegant original method.

In this paper we develop a redshift space variational method,apply it to a small system —the Local Group —,and point out the algorithmic problems that need to be solved to extend to larger systems.

Various aspects of the Local Group dynamics have been studied by Peebles (1989),Peebles (1990),Peebles (1994),and Dunn and La?amme (1993).The new feature of our analysis is that we attempt to constrain the masses of the Milky Way,M31,and an underlying distribution of un-clustered matter by using a likelihood approach.

Two points need to be made about these variational methods in general:Firstly,the true solutions of the vari-ational action need not be a minimum even though the col-loquial use of ‘least action’has stuck (cf Peebles (1990)).Secondly,the equations solved are the same as for N -body integration,only the approximations used to solve them are di?erent.In neither of the two approaches do parti-cles have to be galaxies –they may well be samplers of some underlying distribution function and as Branchini

1

2Variational Dynamics and the Local Group

and Carlberg (1994)and Dunn

and La?amme (1995)have pointed out,applying the variational method using galax-ies only,neglecting biasing and unclustered matter,leads to wrong results.

2.FORMULATION

Orbits of galaxies follow equations of motion of the form

d

?x ,

(1)

where x are some comoving coordinates,and a (t )is the

scale factor of the universe.These equations are deriv-able from a stationary action,δS =0,subject to some boundary conditions.In this work,we will distinguish be-tween two di?erent actions and di?erent sets of boundary conditions leading to the same equations of motion.

2.1.Two Kinds of Boundary Condition

For simplicity,let x be one-dimensional in this subsec-tion.Then the two cases are:

?the ‘real space’case,where the boundary conditions are a 2˙x =0at t =0(i.e.,initial peculiar velocities zero)and δx =0at t =1(i.e.,present positions ?xed)with the action given by

S =

1

Ldt ,where L =

1

2a ˙ax

2(3)

and L remains the same.Whiting (1998)describes

more general transformations of this type.

The standard method for ?nding an orbit that will keep the action stationary and therefore is a solution to the equations of motion consists of formulating a parametric expression for the coordinates x which satis?es the bound-ary conditions and adjusting the parameters to make the action stationary.For the real space case,we choose the expression

x =N n =1

C n f n (t ),(4)

where C n are a series of N coe?cients and f n (t )is a tem-poral basis function.For the redshift space case,

x =

cz

˙a (1)

,g n>1(t )=f n (t )(6)

A good choice for f n is (1?D (t ))n ,where D (t )is the growth factor from linear theory;this was proposed by Gi-avalisco et al.1993.In this case,for N =1the variational method reduces to linear theory.But all that is essential is that linear theory should be followed as t →0.So,other choices such as f n =(1?t 2/3)n are also possible.

2.2.Equations for Stationary Action

The real three-dimensional problem is a combination of the two types of boundary conditions.Because of the way in which we choose coordinate systems,the real space treatment can be used for the ?rst two dimensions (x ,y )of each orbit and only the third dimension (z )will have to be treated in redshift space.We will refer to axes by their dimension rather than by a x ,y ,or z in order to prevent confusion between the third dimension and the symbol used for redshifts.

One coordinate system is assigned to each object and all coordinate systems share a common origin.This ori-gin is the point from which a comoving observer would measure the objects’redshifts.It is important to note that,although the objects move,their coordinate frames do not.By pointing the 3-axis of each frame towards the current galactic coordinates l ,b of the object associated with it,we ensure that the radial velocity is along one axis only.Therefore,the redshift space treatment will have to be applied only to that axis.With this orientation,

the 3-coordinate of each object is cz i (cz i =˙ax i 3+a ˙x

i 3),where z i is the ‘comoving’redshift,i.e.the redshift mea-sured by an observer who is at rest with respect to the microwave background.The 1,2-coordinates at t =1are x i 1=0,x i 2=0,so the current positions are completely speci?ed and real space treatment can be applied.

In these coordinates,the parametric expansion of the position x of an object i becomes

x i (1,2)=

N

n =1

C i (1,2),n f n (t )

(7)

x i (3)=

cz

2

i

m i a ˙x 2i ?

1

a

i,j

m i m j

2a ˙ax

2i (3)

.(10)

The ?rst term in equation 9describes the total kinetic

energy,the second term is an acceleration caused by the fact that the coordinate system is expanding at a rate a (t ),

I.Schmoldt,P.Saha3 and the third term describes the gravitational interaction

between members of the group of objects.Φtidal repre-

sents the tidal potential caused by the in?uence of objects

external to the region considered.Note that introducing

a homogeneous mass distribution into the system is very

easy since it will only rescale the second term.

Inserting the equations9and10into the action S and

taking the gradient with respect to the C i leads to

1

0a2˙f m˙f n dt C i(1,2),n=

1 0f n

?C i

(1,2)

(11)

and

˙f

1

(1)2

˙a(1)=

g n?C i

(3)

(12)

To?nd the orbits which keep the action stationary,we now have to solve equations11and12for the spatial coef-?cients C i,n.The standard method is to assume some ini-tial coe?cients,calculate the right hand sides,then solve the left hand sides for the coe?cients and use the results to recalculate the right hand sides.Note that the left hand side integrals in equations11and12have to be done only once.

We have experimented with various procedures to

help convergence, e.g.adding a stabilising term∝ ¨a af m f n dt C i,m on both sides of the equation or scaling down some terms for early iterations and only slowly in-creasing them to their full value(cf Susperregi and Binney (1994),Giavalisco et al.1993).

2.3.Units

It is convenient to de?ne model units for time,mass, and length(tick,marble,and lap)which we keep scaleable with the age of the universe T0,since T0is not known.The units are given by

1tick=T0=10κGa(13)

andκis the age of the universe in units of10Ga.We do not want the velocities to be scaleable,so we require 100km/s=1lap/tick which leads to

1lap=1.023κMpc(14)

The assumption of a gravitational constant equal to unity as in the equations above leads to

1marble=2.38·1012κM⊙(15)

We therefore have a one-parameter family of models for di?erent ages of the universe.

3.APPLICATION TO THE LOCAL GROUP

In this section we will apply the above formalism to a small group of galaxies,namely the Milky Way–M31 system and outlying Local Group dwarves,with external forces approximated by dipole and quadrupole tidal forces growing according to linear theory.Since distances to ob-jects within this group are fairly well known,we can con-strain the mass distribution by comparing the distances predicted by our method to the observed distances for a range of di?erent mass distributions.We also test the ef-fects of assuming di?erent values for?0.

3.1.Formulation for the Local Group

The formalism is outlined in section2,but for the Local Group there are two special considerations:

Firstly,the Milky Way has a special role.As explained above,each galaxy has its own coordinate system,and we take the current position of the Milky Way as the com-mon origin.This origin is at rest with respect to the CMB and for t=1the Milky Way moves away from it.As the Milky Way’s current position is?xed the real space treatment can be applied in all three dimensions. Secondly,cosmology only in?uences the Local Group via tidal forces.Therefore,we can keep things simple by in-troducing the following complication:The integrals on the left hand sides of equations11and12are particularly simple to solve for a(t)=t2/3,and we exploit this fact by setting a(t)=t2/3regardless of cosmologies.This a(t)is only the scale factor of a convenient frame that we have chosen for the Local Group and which need not necessar-ily bear any relation to the real physical scale factor of the universe a phys(t)except at the boundaries

a(t→0)=t2/3∝a phys(t→0)

a(t=1)=1=a phys(t=1)(16)

For interactions between members of the group,the value of a(t)does not matter.Only when calculating the in-?uence of the tidal forces do we have to consider the relation between the two sets of comoving coordinates x phys=a

a phys d·x phys+1

4Variational Dynamics and the Local Group

3.2.Finding Solutions in the Local Group

We model the Local Group as an ensemble of 13galax-ies with the mass of the system distributed between the Milky Way,M31,and some local unclustered matter ρsm .It is convenient to express this ρsm in units of the critical density,but it is important to note that it is only local and does not change the cosmology.The cosmological models have Λ=0and various ?0.The ratio of masses of Milky Way and M31is ?xed at 2:3and all dwarf galaxies are treated as test particles.

We select the dwarf galaxies by choosing all objects from the list of Local Group members (Hodge et al (1993))which are more than 500kpc away from both M31and the Milky Way.This high distance is a necessary restriction because the orbits of nearby galaxies tend to be too dom-inated by the internal dynamics of the Milky Way–M31system and are therefore di?cult to reconstruct.Nearby galaxies might also be part of the system’s halo.The dwarf galaxies chosen,on the other hand,are generally not too sensitive to the mass ratio between M31and the Milky Way because of their relatively great distance to that sys-tem.Distances (from Hodge et al (1993))and redshifts (from the Nasa/IPAC Extragalactic Database)of all galax-ies are listed in table 1.Note that these heliocentric red-shifts are converted to CMB–centric redshifts to get the appropriate boundary conditions.

Galaxy l b cz

d obs d model deg deg km

M31121.2-21.6-300725787IC1613129.8-60.6-234765498WLM 75.9-73.6-1169401224Sextans A 246.239.932413001878N3109262.123.140312601977IC10119.0-3.3-34412501227Pegasus 94.8-43.5-183********Sextans B 233.243.830113002023SagDIG 21.1-16.3-7711501266LGS 3

126.8-40.9-2777601220EGB0427+63144.710.5-998002069N6822

25.3

-18.4

-57

540

1554

˙a (1)

.(18)

This produces an initial set of x i (t )which ?t the red-shifts and measured distances (if 1lap =1Mpc)but

which are not solutions of the equations of motion.We therefore add an extra term to equations 11and 12to change them into something that the x i are solutions of.This term is then gradually removed from the equations during iteration.

Our current method always produces convergence of the coe?cients,but does not do so in a very e?cient way.In most cases,we need several hundred iterations to achieve convergence,where the main problem seems to be that some of the converging C i,n are caught in a cycle of two

values.We have tried to remedy this problem in a very crude way and were successful but only at a severe cost in iterations;this is one of the problems that will have to be solved in a more general way,before the code can be applied to large datasets.

We check our reconstructed x i by taking their values at t =0.01as the initial conditions of an N -body integration.Figure 1shows the variational orbits and N -body orbits for a system of a total mass of 3.10marbles.For the mass distribution of table 1,the dipole acceleration inferred is 0.85laps /tick 2in the direction l =274?and b =29?(the direction is indistinguishable from Yahil,Tammann,and Sandage (1977)).

Figure 1.Variational and N -body orbits for ?=0.99,m tot =3.10marbles (no unclustered matter);squares indicate positions at t =1;the scale is in comoving laps and the coordi-nate directions are (cos b cos l,cos b sin l,sin b ).We have labelled as many of the galaxies as was possible without overcrowding the ?gure.

The last column of table 1lists the predicted distances for this particular model.They are generally similar to the measured distances,which is not a trivial result,since as far as the mathematical formalism is concerned,the pre-dicted distances are not even constrained to be positive.In fact,when trying to reconstruct the orbits of galaxies which are too close to M31or the Milky Way,the code does produce negative distances.A typical example of this is Leo I (cf Zaritsky et al (1989)):the code is given a pos-itive redshift but only ?nds approaching solutions.The only way to reconcile these two requirements is to put the dwarf galaxy on the other side of the Milky Way -which is what produces the negative distance.The reason for this is that nearby galaxies are too dominated by halo dynam-ics and we have not attempted to model the halo in any way.Hence our decision to exclude all the nearer dwarf galaxies.

3.3.Analysis of Local Group Solutions

To quantitatively analyse our results,we assign a like-lihood to each set of solutions and therefore to each mass distribution.The following is very crude,but we decided to use it because it is well de?ned and uses plausible reasoning.The likelihood is calculated in the standard Bayesian fashion by assessing the probability of a set of solutions given the set of measured distances.We have to allow for the uncertainties associated with the measured

I.Schmoldt,P.Saha

5

distances,and the fact that some of our solutions might simply be wrong (we call this the ‘outlier probability’).As we have no particular reason to believe that the uncertain-ties in d obs are Gaussian,we use (for all galaxies except M31)the hatbox function

hb(x,a,b )=

(b ?a )?1if a ≤x ≤b

0otherwise If the outlier probability is αand the uncertainty in d obs

is βthen

prob(d i obs |d i

model )=αhb (d obs ,min(d obs ),max(d obs ))+(1?α)hb d i obs ,(1?β)d i obs ,(1+β)d i

obs

(19)For M31we take prob(d i obs |d i

model )to be Gaussian where the observed distance has an associated uncertainty of 5%.

Combining all galaxies,we have,

prob(data |model,α,β)=

i

prob(d i obs |d i

model ,α,β)

(20)

Since we do not know αor β,we marginalise by inte-grating over a plausible range of both with a suitable prior,i.e.we integrate over 0.1≤α≤0.3with a ?at prior and 0.1≤β≤0.3with a 1/βprior.

Figure 2shows likelihood contours for two di?erent val-ues of ?0

.

Figure 2.Likelihood contours for variational solutions asso-ciated with di?erent mass distributions:above ?=0.4,below ?=0.99In both cases,κ=1.Contour levels di?er by a factor of 10.

Masses are particularly high for low ?0because the quadrupole force,which pulls the Milky Way and M31apart is higher in those cosmologies and so we require more mass to keep the two galaxies at the same distance from each other.

The likelihood contours are dominated by M31:leav-ing one or more of the dwarf galaxies out of the likeli-

hood analysis does not make a lot of di?erence to the con-tours whereas leaving out M31severely limits the state-ment that can be made about the mass of the system.In

the ?0=0.99universe,for example,we can only say that the combined mass of the system is probably less than 9×1012M ⊙.

Figure 3shows the same contours as ?gure 2but for the case of an older universe.The masses generally decrease in this case,because less mass is needed to produce the same results when gravitation works over a longer period in

time.

Figure 3.As for ?gure 2but with κ=1.5.

Both ?gure 2and 3were produced from a set of solu-tions using 8basis functions.We experimented with dif-ferent numbers of basis functions but the results remain

the same.

Our results indicate that most of the physics are in-cluded in our model if not all of them.Hence we opted for a likelihood analysis.The analysis shows the system domi-nated by M31,which makes our model not so very di?erent from the one used for the timing argument.However,if we leave M31out of the analysis,the resulting contours are at least consistent with ?gures 2and 3.There seems to be some slight preference for mass to cluster with the galaxies,but the contours are not really conclusive.

4.DISCUSSION

The N -body check proves that the code works and is ready to be extended to larger systems.The main prob-lem with a system like the Local Group is the occurrence of multiple solutions.We have no guarantee that the solu-tions we ?nd are the real ones,even if they ?t all redshifts perfectly and predict distances which are not too far out from the measured ones.In fact,some tests suggests that at least for certain masses,several possible solutions are very close to each other so it is easy to pick the wrong one.This problem will not occur in larger systems,so they should in fact be easier to deal with.

6Variational Dynamics and the Local Group

In future work,two issues will need to be addressed: First,we need an approximate and more e?cient way of doing the force calculations in equations11and12.The direct sum that we have used needs to be replaced by a standard N-body method.Second,we need more e?cient convergence.As mentioned above,the main di?culty lies in preventing the coe?cients from?nding two-cycles in-stead of?xed points of the iteration.A faster yet still robust method for dealing with this problem is needed. Even when these problems are solved,the variational calculations will never have as many particles as N-body simulations.The reason for pursuing this method is that unlike the N-body calculation,which can only reproduce the current state of the system in a statistical sense,the variational method can?t the current state exactly.

The authors would like to thank Alan Whiting and James Binney for many helpful comments and suggestions.

I.S.acknowledges a PPARC studentship and an Oriel Col-lege graduate scholarship.

REFERENCES

Branchini,E.,Carlberg,R.,ApJ434,37(1994)

Buchert,T.,Ehlers,J.,1993,MNRAS,264,275

Dunn,A.M.and La?amme,R.1993,MNRAS,426,865

Dunn,A.M.and La?amme,R.1995,ApJ,443,L1

Giavalisco,Mancinelli,Mancinelli,and Yahil(1993),ApJ,411,9 Gramann,M.1993a,ApJ,405,449

Gramann,M.1993b,ApJ,405,L47

Hodge,P.1993,Proceedings of V Canary Islands Winter School of Astrophysics,Ed.Sanchez,F.,Munoz-Tunon,C.,Cambridge Uni-versity Press,ISBN052149575X

Kogut et al.,ApJ,419,1

Nusser,A.,Dekel,A.,1992,ApJ,391,443Peebles,P.J.E.1989,ApJ,344,L53

Peebles,P.J.E.1990,ApJ,362,1

Peebles,P.J.E.1994,ApJ,429,43

Raychaudhury,S.,Lynden-Bell,D.,MNRAS,240,195

Shaya,Peebles,and Tully,Conf.Cosmic Velocity Fields(Paris,July 93)

Shaya,Peebles,and Tully,ApJ,454,15

Susperregi,M.,Binney,J.MNRAS271,719(1994)

Whiting,A.B.,ApJ,(submitted)

Yahil,Tammann,and Sandage,1977,ApJ,217,903

Zaritsky,D.,Olszewski,W.,Schommer,A.R.,Peterson,R.C.,and Aaronson,M.ApJ345,7591989

英语介词用法大全

英语介词用法大全 TTA standardization office【TTA 5AB- TTAK 08- TTA 2C】

介词（The Preposition）又叫做前置词，通常置于名词之前。它是一种虚词，不需要重读，在句中不单独作任何句子成分，只表示其后的名词或相当于名词的词语与其他句子成分的关系。中国学生在使用英语进行书面或口头表达时，往往会出现遗漏介词或误用介词的错误，因此各类考试语法的结构部分均有这方面的测试内容。 1. 介词的种类 英语中最常用的介词，按照不同的分类标准可分为以下几类： (1). 简单介词、复合介词和短语介词 ①.简单介词是指单一介词。如： at , in ,of ,by , about , for, from , except , since, near, with 等。②. 复合介词是指由两个简单介词组成的介词。如： Inside, outside , onto, into , throughout, without , as to as for , unpon, except for 等。 ③. 短语介词是指由短语构成的介词。如： In front of , by means o f, on behalf of, in spite of , by way of , in favor of , in regard to 等。 (2). 按词义分类 {1} 表地点（包括动向）的介词。如： About ,above, across, after, along , among, around , at, before, behind, below, beneath, beside, between , beyond ,by, down, from, in, into , near, off, on, over, through, throught, to, towards,, under, up, unpon, with, within , without 等。 {2} 表时间的介词。如： About, after, around , as , at, before , behind , between , by, during, for, from, in, into, of, on, over, past, since, through, throughout, till(until) , to, towards , within 等。 {3} 表除去的介词。如： beside , but, except等。 {4} 表比较的介词。如： As, like, above, over等。 {5} 表反对的介词。如： againt ,with 等。 {6} 表原因、目的的介词。如： for, with, from 等。 {7} 表结果的介词。如： to, with , without 等。 {8} 表手段、方式的介词。如： by, in ,with 等。 {9} 表所属的介词。如： of , with 等。 {10} 表条件的介词。如：

表示地点的介词

表示地点的介词 in、on、behind、next to、near、over、under (1) in在……里面：The pencil is in the desk. 铅笔在课桌里。 (2) on在……上面：There are some apple on the tree. 树上有些苹果。 (3) under在……下面/正下方：What's under your desk? 你书桌底下是什么？ (4) over在……正上方：There is a shelf over the table. 桌子上方有一个书架。 (5) above 在……斜上方：Raise your arms above your head. (6) below 在……斜下方：Her skirt came below her knees. (7) behind在……之后：There is a bike behind the tree. 树后有一辆自行车。 (8) next to在……旁边：There is a shop next to the school. 理发店隔壁是一家咖啡馆。 (9) near在……附近：My bed is near the window. 我的床在窗户旁。 (10) by在……旁：He was sitting by the window. (11) beside 在旁边He sits down beside Jim. 一组：over, above和on的用法 1) over指在…的正上方，表示垂直在上。如 There is a lamp over the desk. 2) above指在上方，属于斜上方。如： Raise your arms above your head. 3) on指在上面，表示两物体接触。如： There is a cup on the table. 二组：under / below的用法： 1) under在……下面/正下方： What's under your desk? 2) below 在……斜下方： Her skirt came below her knees 三组：in 和on表示“在……上” 1)门/窗一类——镶嵌在墙里的，用in; 2)字画一类——挂/贴在墙面上的，用on ( ) 1 He put up a map ___ the back wall because there was a hole ______ it. A. on; on B. at; in C. on; in D. on; at ( ) 2 There is a door___ the wall. A. on B. to C. of D.in 3)人/鸟其他东西在树上，用in; 4)枝叶果实长在树上的，用on ( ) 1 There are some birds singing___ the trees. A. in B. on C. at D. from ( ) 2 There are so many apples___ that tree. A.in B, on C of D.from

初中英语考点 in_on_at_区别用法

in on at 区别用法 妙计口诀 1.早、午、晚要用in， at黎明、午夜、点与分。 年、月、年月、季节、周， 阳光、灯、影、衣、帽用in。 将来时态in...以后， 小处at大处in。 有形with无形by， 语言、单位、材料in。 特征、方面与方式， 心情成语惯用in。 介词at和to表方向， 攻击、位置、恶、善分。 2.日子、日期、年月日，星期加上早、午、晚， 收音、农场、值日on，关于、基础、靠、著论。 着、罢、出售、偷、公、假，故意、支付、相反，准。 特定时日和“一……就”，on后常接动名词。 年、月、日加早、午、晚，of之前on代in。 步行、驴、马、玩笑on，cab，carriage则用in。 at山脚、门口、在当前，速、温、日落、价、核心。 如大体掌握上面介词用法口诀，就不易出错。下面对该口诀分别举例帮助你理解消化。 <1.>关于时间 早、午、晚要用in in the evening 在晚上 in the day 在白天 例： in the afternoon 在下午 in the morning 在早上 at黎明、午、夜、点与分 例 at dawn /at daybreak 在黎明时候 at night 在夜间 at noon 在中午 at midnight 在午夜 （以上短语都不用冠词）

at nine o'clock 在9点钟 at half past ten 在10点半 at ten thirty a.m. 在上午10点30分 at the weekend 在周末 at a quarter to two 1点45分 <2.>关于年、月、年月、季节、周 即在“来年”，在“某月”，在“某年某月” 但在某年某月某日则用on ，在四季，在第几周等都要用in。 in 1927 在1927年 in March 在三月 in December 1986 在1986年12月 in July l984 在1984年7月 in the first week of this semester这学期的第一周 in the third week 在第三周 in spring 在春季 <3.>关于日子、日期、年月日，星期加上早午晚 以下皆用on on October the first 1949 1949年10月1日 on May the first 5月1日 on the sixteenth 16号 on the second of January /on January the second 1月2日 on a summer evening 在夏天的一个夜晚 on New Year's Day 在元旦 on my birthday 在我的生日 on winter day 在冬天 on December 12th 1950 l950年12月12日 on Sunday 在星期天 on Tuesday morning 星期二早晨 但last night 昨夜；in the evening 在晚上 on time准时，in time及时，等则不同。 【注】in the Christmas holidays在圣诞节假期 in the eighteenth century 在十八世纪 in ancient times 在古代 in earlier times 在早期 in modern times 在现代，则用in，at the present time 现在，at the present day当今则用at。 <4.>关于年月日，加早午晚，of之前on代in on the morning of 18th 18日早晨 On the eve of their departure在临行前夕 <5.>阳光、灯、影、衣、冒 in

介词的用法

（一）介词概述 介词是一种虚词，在句子中不单独作任何句子成分。它是一种表示名词和句中其他词之间关系的词。它常和名词、动词、形容词等搭配，构成固定短语，表示不同意思。介词还可以与名词构成介词短语，表示方位、方向、时间、地点、方式、原因等。这些介词短语在句中可充当定语、状语、补语等。2000—2005年的中考中主要考了形容词与介词的搭配：如：be famous for；表示时间的介词，如：at night；动词与介词的搭配，如：arrive in/have dinner with sb.；表示方式、手段的介词，如：by phone/in English. （二）基础知识梳理 1．名词与介词的搭配 a bit of有一点儿 a couple of两个、几个 a kind of一种、一类cover an area of占地面积 have pity on sb.怜悯某人huge amounts of大量的 make friends with与……交朋友make fun of拿……开玩笑 meet the needs of迎合……的需要one after another一个接一个；连续地 play a trick on捉弄the week after next下下周 2．动词与介词的搭配 agree with sb.同意某人的意见apologize to sb. for sth.为某事向某人道歉arrive at/in a place到达某地ask for请求、寻求 be covered with被……所覆盖be made of由……制成 be made up of由……组成belong to属于 break into破门而人、闯入 call on拜访 care for照顾、喜欢carry out执行 check in办理登机come across被理解；遇见 come from出生于、来自come on跟我来、走吧

地点和位置的介词

表示地点和位置的介词 1.at, in, on 1) at 表示较狭窄较小的地方（小村庄，小城镇），in 表示较大的地方（大城市，大的空间）。 I met her at the bus-stop. They arrived at the famous town in South Jiangsu. She is living in Nanjing. There are a great many islands in the Pacific. 2) 门牌号码前用at，road前面用on，street前用in或on。 in the street (BrE) on the street (AmE) at 103 Wall Street on the road 3) 把某个机构看成是机关或组织时用at，看成一个具体的地方时用in She is at Oxford. 她在牛津读书。She is in Oxford 她在牛津居住（工作或逗留） 4）at可以表示有意、有目的的行为。 She is at the table. 她在吃饭She is beside/ by the desk. 她坐在桌旁。 5) on 在---上面，表示上下两者紧贴在一起，in 表示在---里面。 She put the book on the desk. She put the book in the desk. She wore a smile on her face. (面部表情) She was wounded in the face. （伤有深度） 2．on 和underneath underneath 是on的反义词，表示某物紧贴在另一物的底下 There is a piece of paper underneath the dictionary. 3.under 和over under 和over 是一对反义词，表示正上方，正下方，没有接触的含义。 There are some chairs under the tree. The lamp hung over the table. under 和over 还可以表示上级、下级。 He is over us= We are under him. 4. above 和below 两者是一对反义词，表示高于、低于，既不表示接触，也不表示上下垂直。 The plane is flying above us. The sun has sunk below the horizon. 5. beneath 可以和underneath, under, below 互换。 6．at, by, beside at 表示有目的的接近、接触，by和beside 表示偶然的接近，不接触。 She will be waiting for you at the school gate at 7 tomorrow. The girl stood by/ beside her mother. To those who stand by me, I shall stand by my promise. 对那些支持我的人，我将恪守诺言。 7．near 和next to Near 表示在---附近，靠近；next to 表示紧挨着，紧靠着。 No birds or animals came near the lake. She went and sat next to him. 8. before, in front of, at the front of, ahead of before 用于某人前；in front of 用于建筑物前；in front of 和ahead of 用于空间可互换，用于时间只能用ahead of；in the front of 表示内部空间的前部；at the front of 表示外部空间

at,in与on的用法区别

at, in与on的用法区别 1. 表示时间，注意以下用法： ①表示时间的某一点、某一时刻或年龄等用at： I get up at six in the morning. 我早上六点钟起床。 He got married at the age of 25. 他25 岁结婚。 ②泛指一般意义的上午、下午或晚上以及月或年等较长的时间，一般用in：We watch TV in the evening. 我们晚上看电视。 He went to Japan in 1946. 他于1946 去了日本。 ③若表示星期几或某一特定的日期，则用on： He left here on the fifth of May. 他于5 月5 日离开这儿。 2. 表示地点、场所、位置等，注意以下用法： ①表示某一点位置，用at： We live at No 87 Beijing Road. 我们住在北京路87 号。 The hospital is at the end of the street. 医院在这条街的尽头。 与名词所有格连用表示地点，也用at。如： at my sister’s 在我姐姐家 at the doctor’s 在医务室 ②表示空间或范围，用in： What’s in the box? 这盒子里有什么? He lives in Paris with his wife. 他同他妻子住在巴黎。 但有时两者可换用：

The meeting was held at [in] the hotel. 会议在宾馆举行。 ③at与in的另一个区别是：at多用于指较小的地方，而in多用于指较大的地方：in Shanghai 在上海at the station 在车站 ④介词on 用于地点，主要指在某物的表面： What’s on the table? 桌上有什么? There’s a wallet lying on the ground. 地上有个钱包。 【注】在少数搭配中，也用介词on： He works on a farm. 他在农场工作。 3. 在某些搭配中，三者的区别与英国英语和美国英语有关： in the street (英) / on the street (美) 在街上 in the road (英) / on the road (美) 在路上 in the team (英) / on the team (美) 在这个队 at the weekend (英) / on the weekend (美) 在周末 at weekends (英) / on weekends (美) 在周末 4. 有时三者的差别与搭配习惯和用法有关： in bed / on the bed 在床上 in the tree (多指树外之物) / on the tree (多指树本身之物) 在树上

常用标点符号用法简表.doc

常用标点符号用法简表 标点符号栏目对每一种汉语标点符号都有详细分析，下表中未完全添加链接，请需要的同学或朋友到该栏目查询。名称符号用法说明举例句号。表示一句话完了之后的停顿。中国共产党是全中国人民的领导核心。逗号，表示一句话中间的停顿。全世界各国人民的正义斗争，都是互相支持的。顿号、表示句中并列的词或词组之间的停顿。能源是发展农业、工业、国防、科学技术和提高人民生活的重要物质基础。分号；表示一句话中并列分句之间的停顿。不批判唯心论，就不能发展唯物论；不批判形而上学，就不能发展唯物辩证法。冒号：用以提示下文。马克思主义哲学告诉我们：正确的认识来源于社会实践。问号？用在问句之后。是谁创造了人类？是我们劳动群众。感情号①！1.表示强烈的感情。2.表示感叹句末尾的停顿。战无不胜的马克思主义、列宁主义、毛泽东思想万岁！引号 ②“ ” ‘ ’ ╗╚ ┐└1.表示引用的部分。毛泽东同志在《论十大关系》一文中说：“我们要调动一切直接的和间接的力量，为把我国建设成为一个强大的社会主义国家而奋斗。”2.表示特定的称谓或需要着重指出的部分。他们当中许多人是身体好、学习好、工作好的“三好”学生。 3.表示讽刺或否定的意思。这伙政治骗子恬不知耻地自封为“理论家”。括号③（）表示文中注释的部分。这篇小说环境描写十分出色，它的描写（无论是野外，或是室内）处处与故事的发展扣得很紧。省略号④……表示文中省略的部分。这个县办工厂现在可以生产车床、电机、变压器、水泵、电线……上百种产品。破折号⑤——1.表示底下是解释、说明的部

分，有括号的作用。知识的问题是一个科学问题，来不得半点的虚伪和骄 傲，决定地需要的倒是其反面——诚实和谦逊的态度。2.表示意思的递进。 团结——批评和自我批评——团结3.表示意思的转折。很白很亮的一堆洋 钱！而且是他的——现在不见了！连接号⑥—1.表示时间、地点、数目等 的起止。抗日战争时期（1937-1945年）“北京—上海”直达快车2.表 示相关的人或事物的联系。亚洲—太平洋地区书名号⑦《》〈〉表示 书籍、文件、报刊、文章等的名称。《矛盾论》《中华人民共和国宪法》《人 民日报》《红旗》杂志《学习〈为人民服务〉》间隔号·1.表示月份和日期 之间的分界。一二·九运动2.表示某些民族人名中的音界。诺尔曼·白求 恩着重号.表示文中需要强调的部分。学习马克思列宁主义，要按照毛泽 东同志倡导的方法，理论联系实际。······

英语中表示时间、地点和位置的常用介词的应用 (自动保存的)

英语中表示时间、地点和位置的常用介词的应用 内容摘要：介词是一种用来表示词与词, 词与句之间的关系的词,在句中不能单独作句子成分。介词后面一般有名词代词或相当于名词的其他词类、短语或从句作它的宾语。介词在英语中有非常重要的地位,但其种类繁多,用法复杂,一个介词还往往有多种意义,本文将从时间、地点和用名词尤其是由动词转化过来的名词的机会较多,而名词与名词之间常常需要介词连接,故英语中使用介词的现象比比皆是。 关键词:表示时间地点和位置附加状语名词动词 内容： 一、英语中表示时间的常用介词 after表示...之后，指某事发生在所指时间后的任意时间，是before的反义词，表示在...之后（1）用在附加状语里，常跟有-ing小句，，如： Li Ming was released from prison after serving three years.李明在服刑三年后出狱。（2）用在名词之后，如：I hate the time after sunset before you come home.我不喜欢日落之后、你回家之前的这段时间。（3）用在动词be之后，如：He turned and went after his brothers.他转身去追赶他的兄弟们。after通常指次序的先后。 in（1）表示在某世纪、年、季度、月、周”以及泛指的上、下午、晚上。如：in the 20th century在20世纪；in 1999在1999年；in winter在冬季；in September在九月；in the morning/afternoon/evening 在上午/下午/晚上。（2）in 过...后(未来时间)，不晚于，如：The train will arrive in three hours.火车三小时到。（3）表示某段时间之后，如：to return in a few minutes/hours/days/months几分钟/几小时/几天/几个月后回来。（4）表示做...时，...发生时，当...时，如：In attempting to save the child from drowning, she nearly lost her own life.她在抢救落水儿童时，自己差点丧命。 注：after与in都可表示“在……之后”，但after后可跟时间段，也可跟时间点；而in后必须跟时间段。after既可用于将来时，也可用于过去时，而in只能用于将来时。I’ll arrive in an hour. 我一小时后到。 during表示在……期间(1)某事在某段时间里连续发生或发生过几次，用在附加状语里，如：During all the years of work, he had been realistic with himself.这些年来在所有的工作中，他总是对自己实事求是。（2）表示某物在某段时间里从开始到结束，都一直得到发展，用在附加状语里，如:I hope this will become clear to you during the course of the lectures.我希望在讲座过程中，你会渐渐明白这一点。（3）指某事在某一期间内的某一刻发生，用在附加状语里，如：The boy disappeared from the hotel during the night.这名男孩在夜间从旅馆失踪。 from表示时间的起点，从……起，多用于“from…to/till…”中。如：You can come anytime from Monday to Friday. 周一至周五你什么时间来都行。from 仅说明什么时候开始，不说明某动作或情况持续多久。 for 表示达...之久（1）过了多少时间，后接“一段时间”，表示某事持续多久，多与完成时连用，如：She has been ill for several days. 她已经病了几天了。（2）表示某事已经发生过一次，用在附加状语里，如：Before using a pan for the first time, wash it with a sponge.在首次使用平底锅前，用

常用标点符号用法含义

一、基本定义 句子，前后都有停顿，并带有一定的句调，表示相对完整的意义。句子前后或中间的停顿，在口头语言中，表现出来就是时间间隔，在书面语言中，就用标点符号来表示。一般来说，汉语中的句子分以下几种： 陈述句： 用来说明事实的句子。 祈使句： 用来要求听话人做某件事情的句子。 疑问句： 用来提出问题的句子。 感叹句： 用来抒发某种强烈感情的句子。 复句、分句： 意思上有密切联系的小句子组织在一起构成一个大句子。这样的大句子叫复句，复句中的每个小句子叫分句。 构成句子的语言单位是词语，即词和短语（词组）。词即最小的能独立运用的语言单位。短语，即由两个或两个以上的词按一定的语法规则组成的表达一定意义的语言单位，也叫词组。 标点符号是书面语言的有机组成部分，是书面语言不可缺少的辅助工具。它帮助人们确切地表达思想感情和理解书面语言。 二、用法简表 名称

句号① 问号符号用法说明。？1．用于陈述句的末尾。 2．用于语气舒缓的祈使句末尾。 1．用于疑问句的末尾。 2．用于反问句的末尾。 1．用于感叹句的末尾。 叹号！ 2．用于语气强烈的祈使句末尾。 3．用于语气强烈的反问句末尾。举例 xx是xx的首都。 请您稍等一下。 他叫什么名字？ 难道你不了解我吗？为祖国的繁荣昌盛而奋斗！停止射击！ 我哪里比得上他呀！ 1．句子内部主语与谓语之间如需停顿，用逗号。我们看得见的星星，绝大多数是恒星。 2．句子内部动词与宾语之间如需停顿，用逗号。应该看到，科学需要一个人贡献出毕生的精力。 3．句子内部状语后边如需停顿，用逗号。对于这个城市，他并不陌生。 4．复句内各分句之间的停顿，除了有时要用分号据说苏州园林有一百多处，我到过的不外，都要用逗号。过十多处。 顿号、用于句子内部并列词语之间的停顿。

英语地点介词的正确使用方法

英语地点介词的正确使用方法 地点介词主要有at ，in，on，to，above，over，below，under，beside，behind ，between。它们的用法具体如下： 1、at （1）at通常指小地方：In the afternoon，he finally arrived at home。到下午他终于到家了。 （2）at通常所指范围不太明显，表示“在……附近，旁边”：The ball is at the corner。球搁在角落里。 2、in （1）in通常指大地方：When I was young，I lived in Beijing。我小时候住在北京。 （2）在内部：There is a ball in in the box。盒子里有只球。 （3）表示“在…范围之内”（是从属关系）： Guangdong lies in the south of China。深圳在中国的南部。 3、on

（1）on主要指“在……之上”，强调和表面接触： There is a book on the table。桌上有一本书。 （2）表示毗邻，接壤（是相邻关系）： Canada lies on the north of America 加拿大在美国的北边（与美国接壤）。 4、to 主要表示“在……范围外”，强调不接壤，不相邻。 Japan is to the east of China。日本在中国的东面。 注意： （1）at 强调“点”，on 强调“面”，in 强调“在里面”，to 表示“范围外”。 （2）on the tree：表示树上本身所长着的叶子、花、果实等 in the tree：表示某物或某人在树上 on the wall：表示在墙的表面，如图画、黑板等 in the wall：表示在墙的内部中，如门窗、钉子、洞、孔 5、above

表示地点位置的介词

表示地点位置的介词 w qsa 1)at ,in, on, to，for at (1)表示在小地方; (2)表示“在……附近，旁边”in (1)表示在大地方; (2)表示“在…范围之内”。on 表示毗邻，接壤，“在……上面”。to 表示在……范围外，不强调是否接壤；或“到……”2)above, over, on 在……上above 指在……上方,不强调是否垂直，与below相对；over指垂直的上方,与under 相对,但over与物体有一定的空间，不直接接触。on表示某物体上面并与之接触。The bird is flying above my head. There is a bridge over the river. He put his watch on the desk. 3)below, under 在……下面under表示在…正下方below表示在……下，不一定在正下方There is a cat under the table. Please write your name below the line. 4)in front [frant]of, in the front of在……前面in front of…意思是“在……前面”，指甲物在乙物之前，两者互不包括；其反义词是behind（在……的后面）。There are some flowers in front of the house.(房子前面有些花卉。) in the front of 意思是“在…..的前部”，即甲物在乙物的内部.反义词是at the back of…（在……范围内的后部）。There is a blackboard in the front of our classroom. 我们的教室前边有一块黑板。Our teacher stands in the front of the classroom. 我们的老师站在教室前.(老师在教室里) 5）beside，behind beside 表示在……旁边behind 表示在……后面 2.表示时间的介词 1)in , on，at 在……时in表示较长时间，如世纪、朝代、时代、年、季节、月及一般（非特指）的早、中、晚等。如in the 20th century, in the 1950s, in 1989, in summer, in January, in the morning, in one’s life , in one’s thirties等。on表示具体某一天及其早、中、晚。如on May 1st, on Monday, on New Year’s Day, on a cold night in January, on a fine morning, on Sunday afternoon等。at表示某一时刻或较短暂的时间，或泛指圣诞节，复活节等。如at 3:20, at this time of year, at the beginning of, at the end of …, at the age of …, at Christmas，at night, at noon, at this moment等。注意：在last, next, this, that, some, every 等词之前一律不用介词。如：We meet every day. 2)in, after 在……之后“in +段时间”表示将来的一段时间以后；“after+段时间”表示过去的一段时间以后；“after+将来的时间点”表示将来的某一时刻以后。3)from, since 自从……from 仅说明什么时候开始，不说明某动作或情况持续多久；since表示某动作或情况持续至说话时刻，通常与完成时连用。since表示"自（某具体时间）以来"，常用作完成时态谓语的时间状语。since liberation（1980）自从解放（1980年）以来They have been close friends since childhood．他们从小就是好朋友。（1）since the war是指"自从战争结束以来"，若指"自从战争开始以来"，须说"since the beginning of the war"。（2）不要将since与after混淆。比较：He has worked here since 1965．（指一段时间，强调时间段）自从1965年以来，他一直在这儿工作。He began to work here after 1965．（指一点时间，强调时间点）从1965年以后，他开始在这儿工作。4)after, behind 在……之后after主要用于表示时间；behind主要用于表示位置。时间名词前介词用法口诀年前周前要用in 具体日子要用on 遇到几号也用on 上午下午得是in 要说某日上下午用on换in记清楚午夜黄昏用at 黎明用它也不错at用在时分前说“差”可要用上to 说"过''要用past 3.表示运动方向的介词： across, through 通过，穿过across表示横过,即从物体表面通过，与on有关，为二

介词的用法及习题

第七单元介词 我们经常在名词或名词短语、代词或动名词前用介词表示人物、事件等与其它句子成分的关系。介词后面的名词或相当于名词的词语叫介词宾语。介词可表示地点、时间、比较、反对、原因、手段、所属、条件、让步、关于、对于、根据等。 二、介词的意义 1．表示时间的介词 in表示“在某一时间段”，或“在……某一时候”，如用在月、季、年份、时代、世纪等时间名词的前面，或用来泛指一天的某一段时间。 In July/summer/2000/ancient times/the 1999’s In the morning/afternoon/evening In也可以指“在……之后”，表示从说话起的若干时间内，如： The bus will be here in ten minutes. On表示“在特定的某一天”，也可用于带有修饰语的一天的某个时间段之前。如： on Saturday, on Saturday morning, on the morning of August 1st at表示“在某一时间点”，或用来表示不确定的时间和短期的假日、时节等。如： at six o’clock, at Easter 介词over, through (out)两者均指“经过的全部时间”。 Stay over the Christmas. 介词for, since for表示动作或状态延续的全部时间长度，为“长达……”之意；since用于指从过去特定的某个时刻到说话时为止的一段时间；两者往往用于完成时。 I have been there for six years. We have not seen each other since 1993. During指“在……时期/时间内”，必须以表示一段时间的词或词组作宾语。 She was ill for a week, and during that week she ate little. 2．表示地点的介词 介词at指小地点或集会场合；on表示线或面上的位置；in表示在立体、区域或环境内，特别是那些教大，能够容纳相应事物的环境。 He works at Peking University. Your radio is on the desk. The boat is in the lake. 3．表示原因的介词 for常常表示褒贬、奖惩的原因或心理原因。 4．表示目的的介词 for表示拟定的接收人或目的；to表示实际的接收人或目的。 I bought the gift for my little sister. I gave the gift to my little sister. 5．表示“关于……”的介词 一般about用于比较随便的谈话或非正式的文体；on用于正式的讲话、著作或报告中；7．表示价格的介词 at和for都可表示价格，at仅表示价格，for还表示“交换”，如： Eggs are sold at 95 cents a dozen here. I bought it for five pounds.

时间地点介词的用法

具体日期前用“on” 注意: 一、含有this, that, these, those, every, each 等的时间状语前不用介词。如： We are going to play football this afternoon. 今天下午我们打算踢足球。 His father goes to work early every day. 他爸爸每天很早去上班。They are working on the farm at the moment. 这几天他们正在农场干活。 二、all day, all week, all year 等由“all +表示时间的名词”构成的时间状语前不用介词。如： We stay at home and watch TV all day.我们整天呆在家里看电视。 三、由“some, any, one等＋表示时间的名词”构成的时间状语前不用介词。如： We can go to the Great Wall some day. 有一天我们会去长城的。 四、时间状语是today, tomorrow, tomorrow morning, tomorrow afternoon, tomorrow evening, the day after tomorrow (后天)等，其前不用介词。如：

What day is it today?今天星期几？ Who's on duty tomorrow? 明天谁值日？ MORE: at 表示时间的某一点 （节日或年龄、瞬间或短暂的时间） Your memory is always poor at this time. （表示一天中的某个时刻不用冠词） I got up at six in the mopning. on 表示某日或和某日连用的某个时间段 You were late on Monday last week. in 用于表示除日以外的某一时间段 （表示年、月、季节、世纪时代） Sorry, I am late, the frist time in May. in和at都可表示地点，而in表示的地点比at所表示的地点大

英语表示地点位置的介词

表示地点位置的介词 1)at ,in, on, to at (1)表示在小地方; (2)表示“在……附近，旁边”in (1)表示在大地方; (2)表示“在…范围之内”。on 表示毗邻，接壤，“在……上面”。 to 表示在……范围外，不强调是否接壤；或“到……” 2)above, over, on 在……上 above 指在……上方,不强调是否垂直，与below相对； over指垂直的上方,与under相对,但over与物体有一定的空间，不直接接触。 on表示某物体上面并与之接触。 The bird is flying above my head. There is a bridge over the river. He put his watch on the desk. 3)below, under 在……下面 under表示在…正下方 below表示在……下，不一定在正下方 There is a cat under the table. Please write your name below the line. 4)in front of, in the front of在……前面 in front of…意思是“在……前面”，指甲物在乙物之前，两者互不包括；其反义词是behind （在……的后面）。 There are some flowers in front of the house.(房子前面有些花卉。) in the front of 意思是“在…..的前部”，即甲物在乙物的内部.反义词是at the back of…（在……范围内的后部）。There is a blackboard in the front of our classroom. 我们的教室前边有一块黑板。Our teacher stands in the front of the classroom. 我们的老师站在教室前.(老师在教室里) 5）beside，behind beside 表示在……旁边 behind 表示在……后面 2.表示时间的介词 1)in , on，at 在……时 in表示较长时间，如世纪、朝代、时代、年、季节、月及一般（非特指）的早、中、晚等。 如in the 20th century, in the 1950s, in 1989, in summer, in January, in the morning, in one’s life , in one’s thirties等。 on表示具体某一天及其早、中、晚。 如on May 1st, on Monday, on New Year’s Day, on a cold night in January, on a fine morning, on Sunday afternoon等。 at表示某一时刻或较短暂的时间，或泛指圣诞节，复活节等。如at 3:20, at this time of year, at the beginning of, at the end of …, at the age

六年级 介词 at、 in与on 用法区别

1、小学英语介词at，in与on在时间方面的用法 at表示时间的一点；in表示一个时期；on表示特殊日子。如： He goes to school at seven o’clock in the morning. 他早晨七点上学。 Can you finish the work in two days. 你能在两天内完成这个工作吗？ Linda was born on the second of May. 琳达五月二日出生。 1. at后常接几点几分，天明，中午，日出，日落，开始等。如：at five o’clock （五点），at down （黎明），at daybreak （天亮），at sunrise （日出），at noon （中午），at su nset （日落），at midnight （半夜），at the beginning of the month （月初），at that time （那时），at that moment （那会儿），at this time of day （在一天的这个时候）。 2. in后常接年，月，日期，上午，下午，晚上，白天，季节，世纪等。如： in 2006（2006年），in May，2004 （2004年五月），in the morning （早晨/上午），in the afternoon （下午），in the evening （晚上），in the night （夜晚），in the daytime （白天），in the 21st century （21世纪），in three days （weeks/month）三天（周/个月），in a week （一周），in spring （春季）。 3. on后常接某日，星期几，某日或某周日的朝夕，节日等。如：on Sunday （星期日），on a warm morning in April （四月的一个温暖的上午），on a December night （12月的一个夜晚），on that afternoon （那天下午），on the following night （下一个晚上），o n Christmas afternoon （圣诞节下午），on October 1，1949 （1949年10月1日），on New Year’s Day （新年），on New Year’s Eve （除夕），on the morning of the 15t h （15日的早上）等。 2、常见的介词 about 大约在……时间 about five o'clock 在周围，大约多远 about five kilometres 关于、涉及 talk about you above 高出某一平面 above sea level across 横过walk across the street对面across the street after 在……之后 after supper 跟……后面 one a fter another 追赶run after you against 背靠逆风 against the wall, against the wind 反对 be against you among 三者以上的中间 among the trees at 在某时刻 at ten o’clock 在小地点 at the school gate 表示速度 at high speed 向着，对着 at me before 在……之前 before lunch 位于……之前 sit before me behind 位于……之后 behind the tree below 低于……水平 below zero 不合格 below the standard by 到……时刻，在……时刻之前 by five o'clock 紧挨着 site by site 乘坐交通工具 by air, by bick被由 was made by us during 在……期间during the holidays for 延续多长时间 for five years 向……去 leave for Shanghai 为了，对于be good for you from 从某时到……某时 from morning till night 来自何方 from New Y ork 由某原料制成be made from 来自何处 where are you from in 在年、月、周较长时间内 in a week 在里面 in the room 用某种语言 in English 穿着in red into 进入……里面 walk into 除分 divide into 变动 turn into water near 接近某时 near five years 在……附近 near the park of 用某种原料制成 be made of 属于……性质 a map of U. S .A