that指人时,相当于who或者whom;指物时,相当于which.在宾语从句中做主语或者宾语,做宾语时可省略.
(5)Thenumberofthepeoplethat/whocometovisitthecityeachyearrisesonemillion.
(6)Whereisthemanthat/whomIsawthismorning?
which指物,在定语从句中做主语或者宾语,做宾语时可省略
(1)Footballisagamewhichislikedbymostboys.
(2)Thisisthepen(which)heboughtyesterday.
when指时间,在定语从句中做时间状语
(1)IstillrememberthedaywhenIfirstcametotheschool.
(2)Thetimewhenwegottogetherfinallycame.
where指地点,在定语从句中做地点状语
(1)ShanghaiisthecitywhereIwasborn.
(2)ThehousewhereIlivedtenyearsagohasbeenpulleddown.
3.why指原因,在定语从句中做原因状语
(1)Pleasetellmethereasonwhyyoumissedtheplane.
(2)Idon’tknowthereasonwhyhelooksunhappytoday.