Relative clauses

Who is for people, which for things, and that for either in a defining clause: the man who called, the book which I read, the car that he bought. Whose shows possession: the girl whose bag was stolen.

A defining clause says which one, and takes no commas: the students who passed will get a prize. A non-defining clause adds extra information between commas, and never uses that: my brother, who lives in Oslo, is visiting.

In a defining clause, you can drop the pronoun when it is the object: the book I read. Where is for places: the town where I grew up.