keep doing,keep on doing這兩個詞組均用來表示“不斷做”的意思,但在涵義上有所不同.
keep doing和keep on doing都可表示“不斷（老是）做某事”的意思,強調(diào)動作連續(xù)不斷,每隔一會兒發(fā)生,這時兩者可以換用.不同的是keep doing中的doing是動名詞,作賓語.例如：John always kept (on) asking questions.約翰總是問個不停.News of successes keeps (on) pouring in.捷報頻傳.
keep doing還可表示連續(xù)不斷的動作或持續(xù)的狀態(tài).keep on doing則沒有這種用法.例如：We kept working in the fields in spite of the rain.盡管下雨,我們還是堅持在地里干活.Why do the dogs keep barking?這些狗為什么不停地叫?
keep up：
堅持不懈