EnglishMain Dictionary
which
Universal Words
pronoun, determiner
1 used in questions to ask sb to be exact about one or more people or things from a limited number:
Which is better exercise-swimming or tennis? * Which of the applicants has got the job? * Which of the patients have recovered? * Which way is the wind blowing?
compareWHAT
2 used to be exact about the thing or things that you mean:
Houses which overlook the lake cost more. * It was a crisis for which she was totally unprepared.
HELPNOTE That can be used instead of which in this meaning, but it is not used immediately after a preposition: It was a crisis that she was totally unprepared for.
3 used to give more information about sth:
His best movie, which won several awards, was about the life of Gandhi. * Your claim ought to succeed, in which case the damages will be substantial.
HELPNOTE That cannot be used instead of which in this meaning.
IDIOMS
which is which used to talk about distinguishing one person or thing from another:
The twins are so alike I can't tell which is which.