被動式:「be(is/was)+past participle(done/cleaned/seen etc.)」,例如:「This room is cleaned every day.」,「This room was cleaned yesterday.」,當我們想知道是誰做或這個動作的原因是甚麼時才用「by」,例如:「This house was built by my grandfather.」,「Two hundred people are employed by the company.」