PREPOSITION IN,ON, AND AT

In many languages, there is only one preposition for the above situations. In English there are three. Just remember that in usually indicates the "largest" time or place, and at usually indicates the "smallest" time or place.




Examples:

A: Where's your office?
B: In Taipei, Taiwan.
A: Really? What part of Taipei?
B: It's on Chung Shan North Road.
A: I know that area. Where exactly is it?
B: It's at 105 Chung Shan North Road, next to the bookstore.

C: When is the wedding?
D: It's in June.
C: What day?
D: It's on Saturday, the 25th.
C: What time?
D: It starts at 6:00.

Prepositions with articles and locations
When talking about locations, use at to indicate the general vicinity or area, and in to indicate inside the building, enclosed area, etc.

For example:
at the swimming pool (on site)            in the swimming pool (in the pool itself i.e. in the water)
at the post office/bank (general)         in the post office/bank (inside the building)
at the zoo (visitors, general area)        in the zoo (animals in their cages)
at school        in the classroom

Sample sentences:
•    I met my wife at the theater. (while watching a movie)
•    I spilled my drink in the theater (on the floor of the building)
•    She works at the library on Wednesdays.
•    She found a rare coin in the library (building).
•    Dr. Jones works at the hospital every day.
•    John was in the hospital for a week with a broken leg.

For school, prison, and church, the is used to indicate the building. No article indicates the general situation. Note the following:

"practice"/situation                                                   buildingin school (studying, listening to teacher, etc.)           in the school (building)
in jail/prison (staying there as a criminal)                 in the jail/prison (temporary)
in church (praying, listening to a sermon, etc.)         in the church (building)
Where's Dad?
in church (attending services)                                    in the church (fixing the windows)
at church        at the church
in prison (He committed a crime.)                              at the prison (visiting his friend)


PRECISE TIME MONTHS, YEARS, CENTURIES and LONG PERIODS DAYS and DATES
•    at 3 o'clock in May on Sunday
•    at 10.30am in summer on Tuesdays
•    at noon in the summer on 6 March
•    at dinnertime in 1990 on 25 Dec. 2010
•    at bedtime in the 1990s on Christmas Day
•    at sunrise in the next century on Independence Day
•    at sunset in the Ice Age on my birthday
•    at the moment in the past/future on New Year's Eve


Look at these examples:
•I have a meeting at 9am.
•The shop closes at midnight.
•Jane went home at lunchtime.
•In England, it often snows in December.
•Do you think we will go to Jupiter in the future?
•There should be a lot of progress in the next century.
•Do you work on Mondays?
•Her birthday is on 20 November.
•Where will you be on New Year's Day?


Notice the use of the preposition of time at in the following standard expressions:
Expression Example :
•    at night The stars shine at night.
•    at the weekend I don't usually work at the weekend.
•    at Christmas/Easter I stay with my family at Christmas.
•    at the same time We finished the test at the same time.
•    at present He's not home at present. Try later.

Notice the use of the prepositions of time in and on in these common expressions:
•    in on
•    in the morning on Tuesday morning
•    in the mornings on Saturday mornings
•    in the afternoon(s) on Sunday afternoons
•    in the evening(s) on Monday evening

When we say last, next, every, this we do not also use at, in, on.
•    I went to London last June. (not in last June)
•    He's coming back next Tuesday. (not on next Tuesday)
•    I go home every Easter. (not at every Easter)
•    We'll call you this evening. (not in this evening)