是
need做情態(tài)動(dòng)詞時(shí)沒(méi)有時(shí)態(tài)的變化,過(guò)去式也是need.后面接動(dòng)詞原形.如：
I need write a letter yesterday.
Need he answer it then?
Yes, he need.
No, he needn't.
情態(tài)動(dòng)詞need表示對(duì)過(guò)去的推測(cè)時(shí)常和現(xiàn)在完成時(shí)連用.如：
You needn't have hurried.你當(dāng)時(shí)不必這么匆忙.
need做實(shí)義動(dòng)詞（行為動(dòng)詞）時(shí),過(guò)去式是needed.后面接to do.如：
I needed to write a letter yesterday.
Did heneed to answer it then?
Yes, he did.
No, he didn't.