need doing 是用v-ing來表示被動(dòng),某物需要被怎樣,比如 The desk needs repairing.
need to do 是是主動(dòng),主語常是某人,某人需要做什么,比如 I need to do the homework now.
以上兩種情況下need都是行為動(dòng)詞.
need做情態(tài)動(dòng)詞時(shí)后面不跟不定式而是直接跟動(dòng)詞原形.
最主要的區(qū)別是：need表示主動(dòng)含義時(shí),肯定句中常做行為動(dòng)詞,也就是加to do. 如: I need to do my homework now.
否定和疑問句中常做情態(tài)動(dòng)詞,加動(dòng)詞原型,否定直接加NOT, 疑問直接提前.
如： Need I tell him the new?
You need not tell him the news.