who用于指人,在从句中作主语或宾语。例如:The boy who is standing there is my brother.(站在那里的男孩是我弟弟。)
which用于指物,在从句中作主语或宾语。例如:The book which I bought yesterday is very interesting.(我昨天买的书很有趣。)
that既可以指人也可以指物,在从句中作主语或宾语。通常在以下几种情况下常用that:先行词是不定代词,如all, everything等;先行词被序数词、形容词最高级修饰等。例如:This is the best movie that I have ever seen.(这是我看过的最好的电影。)