as if / though引导表语从句时，在句子中也不充当任何成分，但有意义。译为：似乎，好像。

He looks as if he were a rich man.

It sounds as if someone is knocking at the door.

他看起来好像是个富翁。

听起来好像有人在敲门。

（三）由从属连词 as if/through引导的表语从句