介詞是一種虛詞，不能獨(dú)立充當(dāng)句子成分，需與動(dòng)詞、形容詞和名詞搭配，才能在句子中充當(dāng)成分。介詞是用于名詞或代詞之前，表示詞與詞之間關(guān)系的詞類，介詞常與動(dòng)詞、形容詞和名詞搭配表示不同意義。介詞短語中介詞后接名詞、代詞或可以替代名詞的詞(如：動(dòng)名詞v-ing).介詞后的代詞永遠(yuǎn)為賓格形式。一、表示時(shí)間的介詞(一)表示時(shí)間段的介詞(1)in , afterin +時(shí)間段，表示從現(xiàn)在起往后推算一段時(shí)間after +時(shí)間段，表示過去某時(shí)間往后推算一段時(shí)間，如：He’ll come back in two days. 但點(diǎn)鐘用after( after three o’clock)He left on July 2 and returned after three days.(2)in , during表示在一段特指的時(shí)間內(nèi)，可用in 或duringThe work was done in / during the holidays.表示年份、月份、季節(jié)用in , 如:in 1999 ,in June , in winter(3)in last, for the past + 時(shí)間段, during表示在最近一段時(shí)間內(nèi)，句中謂語動(dòng)詞常用現(xiàn)在完成時(shí)I have been in Shanghai in the last few years.(4)for 表示延續(xù)一段時(shí)間。I’ll study in the U.S for two yearsI’ve waited for Bingo for half an hour.(二)表示某一時(shí)間的介詞(1)at, onat 表示某一時(shí)刻，on 表示某一天或日期, 如:at 7:14, on Saturday morning on the night of May2一天內(nèi)各段時(shí)間表達(dá), 選用正確的介詞，請(qǐng)比較：in the morningon a winter / snow / cold / morningat nighton the night of March 7thin the eveningon Friday evening(2)before, bybefore 表示某一時(shí)間之前，而by 表示到某一時(shí)間止，句中謂語動(dòng)詞多用完成時(shí)態(tài)。如:：You must get up before six. 你必須六點(diǎn)之前起床。By the end of last month the boy had got 4 “As”.到上月底這個(gè)男孩已得了4個(gè)A.
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