1. 先行詞為人 who(主格)+V whom(受格)+S+Vt / S+Vi+prep whose(所有格)+N+(S)+V 2. 先行詞為物或事 which(主格)+V which(受格)+S+Vt / S+Vi+prep whose / of which(所有格)+N+(S)+V 3. that 可以代替 who, whom 及 which。 4. 先行詞為獨一無二的人,物或事時用補述用法,要用逗號撇開,不可用 that;反之則用限定用法,不須逗號撇開,作受格時 whom 或 which 或 that 可省略之。 例句: 1. 上個禮拜三搶劫銀行的嫌疑犯仍然逍遙法外。 The suspects who/that robbed the bank last Wednesday are still at large. 2. 姑媽送給我一只她在瑞士買的錶。 My aunt sent me a watch (which/that) she bought in Switzerland. 3. 大衛是我的小學同學,昨天我在街上巧遇他。 David, whom I met by chance yesterday, was my elementary school classmate. from http://www.nani.com.tw/slearn/sleng/eng_d/Chapter09/Chapter09_4.htm