Basic English Usage
Prepositions are used to show a relation between two things. That relation can be specific, such as location or time. Or it can be abstract, such as cause or means.
To use prepositions correctly, we rely on customs of usage, not rules. The idioms of English prepositions must be learned little by little. Sorry about that.
Three small prepositions cause the most trouble: in, on, at. They are used by themselves or combined with other words in many different ways. Depicted here, however, is a visual memory aid that shows the general differences between them:
These prepositions can be used to indicate "Where":
We met in Ottawa on the Rideau Canal at the Corktown Footbridge.
We talked in a Tim Horton's on Elgin Street at the Courthouse.
They can also be used to indicate "When":
We met in February on a Saturday at 10:15 a.m.
We talked in 2017 on the last day of Winterlude at noon.
Exceptions! It just never ends, right? Again, sorry. We do not use in, on, or at in front of certain words that indicate ordering or selection, including next, last, this, and every.
We will not meet on Wednesday; instead, we will meet next Thursday.
We did not meet last Tuesday; I'm sure we met on Monday.
I will not call you at noon; instead, I will call you this evening.
I do not visit the canal on weekdays; instead, I visit the canal every weekend.
Even more exceptions?! You bet. I'll stop apologizing now. We do not use in, on, or at in front of tomorrow or yesterday.
I will contact you tomorrow.
I visited the canal yesterday.
Course: Basic English Usage