amerikai:
brit:
1. (interrogative) What one or ones (of those mentioned or implied).
By now, you must surely know which is which.
2. The/Any ones that; whichever.
Please take which you please.
3. (relative) Introduces a relative clause giving further information about something previously mentioned.
He had to leave, which was very difficult.
4. (relative) Used of people (now generally who, whom or that).