1. used to ask for information specifying one or more people or things from a definite set
Usage: interrogative
2. used to introduce a clause giving further information about something previously mentioned
Usage: relative pronoun

1. asking for information specifying one or more people or things from a definite set
Usage: interrogative
2. used to be specific about the thing or things being referred to
Usage: relative

Examples

• Which book do you want to read?
• I don’t know which way to go.
• The house, which was built in 1920, needs repairs.
• She showed me the photos which she took on vacation.
• Which color do you prefer, blue or green?
• The decision, which was made yesterday, surprised everyone.
• Which students are going on the field trip?