=thesecond/theminute/themoment/theinstant…
Eg.Hecamearoundtoseemeassoonas/themoment/immediatelyhecheckedinthehotel.
他刚一入住宾馆就来看我.
Theyinformedusthenewsimmediately/directlytheygotit.
他们一得到消息就通知了我们.
Thepolicemancametothespotthemoment/theinstant/theminutesheheardoftheaccident.一听说事故，这位警察就到了现场.
2.….before….
(1).没来得及…就…
Therooffellbeforehehadtimetodashintotheroomtosavehisbaby.
他还没有来得及冲进房间把孩子就出来，房顶就塌了.
HeranoffbeforeIcouldstophim.
Tomygreatdisappointment，myfavoritesingerlefttheconcertbeforeIcouldhaveawordwithhim.
(2).过了多久才怎么样，动作进行到什么程度才怎样
Theywalkedaboutthirtymilestothewestbeforetheysawavillage.
Theyworkeddayandnightaboutthreedaysbeforeeverythingreturnedtonormal.
ThreeyearspassedbeforeIknewit.
3.Itwas+时间段+before….过了多久才….；
Itwasnotlongbefore…不久就…
Itwill(not)be+时间段+before…要过多久(不久)…..才…..
Eg.Itwasnotlongbeforehesensedthedangeroftheposition.
Itwasthreeyearsbeforehecameback.
Itwillbehalfayearbeforeyougraduatefromthisschool.
4.nosooner…than…=hardly…when…一…就….，刚刚…就…
Nosooner/hardly+过去完成时，than/when+一般过去时
如果nosooner，hardly位于句首，主句要倒装.
HehadhardlysatdowntohavearestwhenthedoorbellrangandincameAllan.
Nosoonerhadhegotoffthetrainthanhisdaughterrantowardshim.
Hardlyhadwearrivedwhenshestartedcryingtogohome.
5.once一旦….，表示时间和条件
Onceyouunderstandthisrule，youwillhavenofurtherdifficulty.
Onceyouhavedecidedtodosomething，youshoulddoitwell.
Onceyouenterthechemistrylab，youshouldfollowtheteacher’sinstructions.
