B1used to add extra information to a previous clause, in writing usually after a comma: That bar on Milton Street, which by the way is very nice, is owned by Trevor's brother.She says it's Charlotte's fault, which is rubbish, and that she blames her.Anyway, that evening, which I'll tell you more about later, I ended up staying at Rachel's place.It's the third in a sequence of three books, the first of which I really enjoyed.He showed me round the town, which was very kind of him.The picking of the fruit, for which work they receive no money, takes about a week.Relative forms