The Difference Between “That” and “Which”
That and which can be translated into Russian as “который” (-ая, -ое), but there is a difference between them.
That defines the word we’re talking about and distinguishes it from others. It often means a unique, one and only object. We can’t take that away from the sentence without losing its meaning.
Example: Is this the train that goes to Brighton? — Это поезд, который идет в Брайтон?
(There’s only one train that goes to Brighton and I need it.)
Which introduces a description of a word and doesn’t limit the meaning of the sentence. It is usually used to add information about the thing just mentioned.
Example: The apple pie which you bought was really nice – where did you get it? — Яблочный пирог, который ты купила, был прекрасен. Где ты его покупала?
General tip: If the information is essential, use that. If it’s just additional information that’s useful but unnecessary, use which.
