The prepositions "at, in and on" are primarily prepositions of:
* place/location
* time
* direction
However, there are other uses for these pronouns, as described below:
At
1. A specific location:.....at 23 Chestnut Street; at the park
2. A point in time:...........at 5 o'clock; at Christmas
3. A condition:................at peace; at war; at rest
4. An activity:.................at work; at school; at play
5. Towards:....................Look at someone; wave at someone
Note: When referring to a specific location or to a point in time, “at” is usually used. When referring to a certain street or a certain day, “on” is usually used. When referring to a location as an area, or when referring to a unit of time longer than a day, “in” is usually used. e.g. at Christmas; on Christmas day; in the Christmas holidays
In
1. Place thought of as an area:.....in London / in Europe
2. Within a location:.....................in the room / in the building
3. Large units of time:..................That happened in March / in 1992.
4. Within a certain time:...............I will return in an hour.
5. By means of:..........................write in pencil / speak in English
6. Condition:...............................in doubt / in a hurry / in secret
7. A member of:..........................He is in the orchestra / in the navy
8. Wearing:.................................the boy in the blue shirt
9. With reference to:....................lacking in ideas / rich in oil
On
1. Touching the surface of:.....on the table / on the wall
2. A certain day:....................That happened on Sunday / on the 6th of June.
3. A certain street:.................on South Street/the store on Main Street
4. About:...............................a book on engineering/a TV show on travel
5. A state or condition:...........on strike / on fire / on holiday
6. By means of:.....................live on a pension / shown on television