Prepositions may be divided into three classes :—

(1) Prepositions which denote Place.

Such are About, above, among, at, before, behind, beside, between, by, down, from, in, into, near, on, through, to, under, up.

We live quite near the post office.

Don’t walk under that tree.

… …. ….

 (2) Prepositions which denote Time.

Such are After, before, by, during, since, till, until.

I must finish this work by five (o’clock).

During the holidays I revise my algebra.

… …. ….

(3) Prepositions which denote a Doer (or Agent), some Cause, Purpose or Reason.

Such are: About, by, for, through.

What is this switch for?

By whom did you send the message?

He failed through carelessness.