A time


Would you please explain when the article “a” could be used with the word “time”.
What are the rules and exceptions?


Student: Can I read with my friend, please?
Teacher: Sorry, only one student is allowed to read at a time.

Thanks for the example.
Are there any others?


“time” is a very common word, used in all sorts of expressions and idioms. It’s hard to know where to start. I suppose most often “a time” means “a period/moment/interval of/in time”, as in “There was a time when we were friends” or “Don’t bother me at a time like this”. If you could give a bit more information about the type of sentence or usage you want to know about, the question may be easier to tackle.