Since引导的从句不论是延续性或非延续性动词，都表示的是动作或状态的完成或结束.
注意一下句子翻译：
SincehelivedinNanjing，Ihavenotheardfromhim.(=sinceheleftNanjing…)
自从他离开南京以来，我没有收到过他的信.
SinceshewasinYangzhou，shehaskeptintouchwithherformerfriends.(sincesheleftYangzhou…)
她离开扬州以来，一直同过去的朋友保持着联系.
对比：
1).Ihaveneverseenhimsincehewasill.
他病好后，我就再也没有见到他.
2).Ihaveneverseenhimsincehefellill.
他生病以后我就再也没有见过他.
Itis/(hasbeen)+时间段+since+过去式
Itis/hasbeentwoyearssincehisfatherdied.
=hisfatherhasbeendeadfortwoyears.=hisfatherdiedtwoyearsago.
他的父亲去世两年了.
Ithasbeen8yearssinceIgraduatedfromuniversity.
=Igraduatedfromuniversity8yearsago.
Itis3yearssincehesmoked.他三年不吸烟了.(即，从句动词延续性的，译成否定意义；从句动词非延续性的，译成肯定意义.)
Itis3yearssinceheleftschool.-----他毕业三年了.
7….until…直到…时候；not…until…直到…才…
Youaretostayhereuntil/tillyourmothercomesback.
Themeetingwasputoffuntilteno’clock.
NotuntilwewatchedtheEarthDayprogramonTVdidweknowmuchaboutglobalwarning.
=WedidnotknowmuchaboutglobalwarninguntilwewatchedtheEarthDayprogram.
=ItwasnotuntilwewatchedtheEarthDayprogramonTVthatweknewmuchaboutglobalwarming.
Notuntilhefailedintheexamdidherealizethathehadwastedmuchtimeplayingcomputergames.
8.…when…引导并列分句，“当时，突然”，强调另一动作的突然发生.
OnedayChuckwasonaflightacrossthePacificOceanwhensuddenlyhisplanecrashed.Chucksurvivedthecrashandlandedonadesertedisland.
IwaswalkingalongtheriverwhenIheardadrowningboycryingforhelp.
Iwasabouttoleavewhenitbegantorain.
对比：A：IwaswalkingalongthestreetwhenIcaughtsightofatailor’sshop.
B：Iwaswalkingalongthestreets.JustatthatmomentIcaughtsightofatailor’sshop.
9.while=although尽管
WhileIadmitthattheproblemisdifficult，Idon’tthinkthatitcan’tbesolved.
WhileIadmithisgoodpoints，Icanseehisshortcomings.
WhileIwasangrywithher，Ididn’tlosemytemper.
10.where地点状语
Youshouldputthebookwhereitwas.
Persistentpeoplebegintheirsuccesswhereothersendinfailure.
Wherethereisawill，thereisaway.
Wheremenaregreedy，thereisneverpeace.
Gowhereyoushould，keeponstudying.
