進行式不定詞

進行式不定詞用來表達動詞或助動詞後持續性的動作,而這些動詞或助動詞必須接不定詞。進行式不定詞的構成為:
to be + 現在分詞

如同現在式不定詞,有些時候必須用上不帶 to 的被動語態不定詞,因此 to 會被省略掉。這種情況會發生在多數情態助動詞後,以及用在其他使用零不定詞的地方。

舉例
  • I'd really like to be swimming in a nice cool pool right now.
  • I happened to be waiting for the bus when the accident happened.
  • It must be nice to be going to a wedding overseas.
  • You must be joking!
  • We should be hurrying. We're late!
  • You'd better be working on your report when I get there.