dressed in a blue uniform and with a rifle over his shoulder

肩扛 步枪 ， 为什么这里用over， over在表示方位的时候 ，应该指 正上方 ，悬空的概念 ，我觉得这里用 on更合适，因为紧贴着肩膀。

请讲解下。谢谢。

over的意义和用法有很多，在你的例句中，over应理解为 "rest on", 步枪靠在肩膀上，个人感觉用over 更贴切地形容了步枪靠在肩膀上的这个动作和状态。

下面是关于 over 这个词的一些解释：

–preposition

1.

above in place or position: the roof over one's head.

2.

above and to the other side of: to leap over a wall.

3.

above in authority, rank, power, etc., so as to govern, control, or have jurisdiction regarding: There is no one over her in the department now.

4.

so as to rest on or cover; on or upon: Throw a sheet over the bed.

5.

on or upon, so as to cause an apparent change in one's mood, attitude, etc.: I can't imagine what has come over her.

6.

on or on top of: to hit someone over the head.

7.

here and there on or in; about: at various places over the country.

8.

through all parts of; all through: to roam over the estate; to show someone over the house.

9.

to and fro on or in; across; throughout: to travel all over Europe.

10.

from one side to the other of; to the other side of; across: to go over a bridge.

11.

on the other side of; across: lands over the sea.

12.

reaching higher than, so as to submerge: The water is over his shoulders.

13.

in excess of; more than: over a mile; not over five dollars.

14.

above in degree, quantity, etc.: a big improvement over last year's turnout.

15.

in preference to: chosen over another applicant.

16.

throughout the length of: The message was sent over a great distance.

17.

until after the end of: to adjourn over the holidays.

18.

throughout the duration of: over a long period of years.

19.

in reference to, concerning, or about: to quarrel over a matter.

20.

while engaged in or occupied with: to fall asleep over one's work.

21.

via; by means of: He told me over the phone. I heard it over the radio.

–adverb

22.

beyond the top or upper surface or edge of something: a roof that hangs over.

23.

so as to cover the surface, or affect the whole surface: The furniture was covered over with dust.

24.

through a region, area, etc.: He was known the world over.

25.

at some distance, as in a direction indicated: They live over by the hill.

26.

from side to side; across; to the other side: to sail over.

27.

across an intervening space: Toss the ball over, will you?

28.

across or beyond the edge or rim: The soup boiled over. The bathtub ran over.

29.

from beginning to end; throughout: to read a paper over; Think it over.

30.

from one person, party, etc., to another: Hand the money over. He made the property over to his brother.

31.

on the other side, as of a sea, a river, or any space: over in Japan.

32.

so as to displace from an upright position: to knock over a glass of milk.

33.

so as to put in the reversed position: She turned the bottle over. The dog rolled over.

34.

once more; again: Do the work over.

35.

in repetition or succession: twenty times over.

36.

in excess or addition: to pay the full sum and something over.

37.

in excess of or beyond a certain amount: Five goes into seven once, with two over.

38.

throughout or beyond a period of time: to stay over till Monday.

39.

to one's residence, office, or the like: Why don't you come over for lunch?

40.

so as to reach a place across an intervening space, body of water, etc.: Her ancestors came over on the Mayflower

–adjective

41.

upper; higher up.

42.

higher in authority, station, etc.

43.

serving, or intended to serve, as an outer covering; outer.

44.

remaining or additional, surplus; extra.

45.

too great; excessive (usually used in combination): Insufficient tact and overaggressiveness are two of his problems.

46.

ended; done; past: when the war was over.

–noun

47.

an amount in excess or addition; extra.

48.

Military. a shot that strikes or bursts beyond the target.

49.

Cricket.

a.

the number of balls, usually six, delivered between successive changes of bowlers.

b.

the part of the game played between such changes.

–verb (used with object)

50.

to go or get over; leap over.

51.

Southern U.S. to recover from.

–interjection

52.

(used in radio communications to signify that the sender has temporarily finished transmitting and is awaiting a reply oracknowledgment.)Compare out (def. 53).

—Idioms

53.

all over,

a.

over the entire surface of; everywhere: material printed all over with a floral design.

b.

thoroughly; entirely.

c.

finished: The war was all over and the soldiers came home.

54.

all over with, ended; finished: It seemed miraculous that the feud was all over with.

55.

over again, in repetition; once more: The director had the choir sing one passage over again.

56.

over against. against (def. 13).

57.

over and above, in addition to; besides: a profit over and above what they had anticipated.

58.

over and over, several times; repeatedly: They played the same record over and over.

59.

over the hill. hill (def. 11).

60.

over there, Informal. (in the U.S. during and after World War I) in or to Europe: Many of the boys who went over there never came back.

61.

over with, finished or done: Let's get this thing over with, so that we don't have to worry about it any more.

it is useful!

1.a bass tuba that coils over the shoulder of the musician.

可套在演奏家肩上的低音大号。

2 a broad cartridge belt worn over the shoulder by soldiers.

背在战士肩上的宽宽的弹药带。

也有on the shoulder的短语 如 It’s the sword on the shoulder, and your destiny is here

无区别

so many explanations.