the mark ( , ) used to separate the items in a list or to show where there is a slight break in a sentence 逗号 The relative clause is separated by commas. 关系从句用逗号隔开。 You need to put a comma before ‘which’. 你需要在“哪个”前面加一个逗号。
Word Originlate 16th cent. (originally as a term in rhetoric denoting a group of words shorter than a colon): via Latin from Greek komma ‘piece cut off, short clause’, from koptein ‘cut’.