Did為一般過去時標誌,它是do的過去時形式,如:
Did you go to see your Uncle in hospital?have當助動詞則為完成時態的標誌,它會根據主語的人稱和單複數發生變化
如:Have you fished your homework?Has she gone to see her father in hospital?
此外,have 還有一個特殊的用法,僅限於美式英語:英式:Do you have a book?美式:Have you a book?若二者同時存在於一個句子中,一般是did在句首 you have the book?你以前有這本書嗎?