Prepositions: In, On, and At

Prepositions with articles and locations

For time and place, IN usually indicates the largest item, and AT indicates the smallest, with ON in the middle. See table below.

Time	Place
IN a country, state, city	IN year, month
ON a street	ON day, date
AT a place	AT (clock) time

Year, Month: In 1999, In December
Country, State, City: In Japan, In Utah, In Taipei
Day, Date: On Saturday, On May 11
Street: On Main Street, On 1st Ave.
Time: At 8:00, At 7:30
Address: At 815 East Main Street

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. ON is between the two.

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Examples:

Q: Where’s your office?

A: In Taipei, Taiwan.

Q: Really? What part of Taipei?

A: It’s on Chung Shan North Road.

Q: I know that area. Where exactly is it?

A: It’s at 105 Chung Shan North Road, next to the bookstore.

Q: When is the wedding?

A: It’s in June.

Q: What day?

A: It’s on Saturday, the 25th.

Q: What time?

A: 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	building
in school (studying, listening to teacher, etc.)	in school (studying, listening to teacher, etc.)
in jail/prison (staying there as a criminal)	in the jail/prison (temporary)
in the school (building)	in the school (building)

Where’s Dad?

“practice”/situation	church
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)