because是从属连词，接表示直接原因的从句，一般放在主句的后面，也可放在主句前面，它表示的语气最强，在回答why的问句时，必须用because。
例如：The swimming pool won't be open today because they're making repairs.游泳池今天不开放，因为他们在修理。
Why did you move to France?你们为什么搬到法国？Because my father found work in Paris.因为我父亲在巴黎找到了工作。
注意：在英语中用了because后，不可再用so。
since 意为"既然"，表示对方已知的无需加以说明的原因或事实，语气比because弱，但是比as 强。
例如：Since we have no money, we can't buy that vase.既然我们没钱，我们就不能买那花瓶。
Since everybody is here, let's begin our party.既然大家都到了，那就开始我们的聚会吧！because是从属连词，接表示直接原因的从句，一般放在主句的后面，也可放在主句前面，它表示的语气最强，在回答why的问句时，必须用because。
例如：The swimming pool won't be open today because they're making repairs.游泳池今天不开放，因为他们在修理。
Why did you move to France?你们为什么搬4．过去分词由原形去字母e后，再双写后面的辅音字母加-en构成（＊例外）hide-hid-hidden ride-rode-ridden write-wrote-written forg et-forgot-forgotten＊5．过去分词由过去式加-n构成break-broke-broken choose-chose-chosen freeze-froze-frozen speak-spoke-spoken steal-stole-stolen6．完全不规则形式am /is-was-been are-were-been fly-flew-flown lie-lay-lain wear-wore-worn二．过去式与过去分词形式相同bring-brought-brought build-built-built buy-bought-boughtcatch-caught-caughtdig-dug-dug feel-felt-felt find-found-foundget-got-gothave /has-had-had hold-held-held keep-kept-kept leave-left-left lay-laid-laid lend-lent-lent lose-lost-lost pay-pa id-paidhear-heard -heard make-made-made mean-meant-meant me et-met-metsay-said-said sell-sold-sold send-sent-sent sit-sat -satsleep-slept-slept smell-smelt-smelt spend-spent-spent spill -spilt-spiltspit-spat-spat spoil-spoilt-spoilt stand-stood-stood swe ep-swept-sweptteach-taught-taught tell-told-told think-thought-thought win -won-wonunderstand-understood-understood wake-woke / waked-woken / wakedshine-shone / shined-shone / shined hang-hung / hanged-hung / hangedlearn-learnt / learned-learnt / learned三．原形、过去式与过去分词三种形式完全相同cost-cost-cost cut-cut-cut hit-hit-hit hurt-hu rt-hurtlet-let-let put-put-put set-set-set shu t-shut-shutread /ri:d/-read /red/-read /red/四．i-a-u变化形式begin-began-begun drink-drank-drunk ring-rang-rung sin g-sang-sungsink-sank-sunk swim-swam-swum五．过去分词与原形相同come-came-come run-ran-run become-became-become六．情态动词（没有过去分词形式）can-could must-must will-would may-mightshall-should1 AAA型（动词原形、过去式、过去分词同形）bet cast cost cut hit打 hurt伤害） let让 put放置read（读）read read rid免除set安置spread (伸展/传播) spread spreadquit放弃quit/quitted，quit / quittedspit吐出spat / spit, spat / spitwet淋湿wet / wetted ,wet / wetted2 AAB型（动词原形与过去式同形）beat（跳动）beat beaten(3) ABA型（动词原形与过去分词同形）become（变成）became become come（来）came comerun（跑）ran run(4) ABB型（过去式与过去分词同形）bend使弯曲bent，bentbring拿来brought，broughtbuild建造built，builtburn燃烧burnt / burned，burnt / burnedbuy买bought，boughtcatch捕捉caught，caughtdeal分配dealt，dealtdig（挖）dug dugdream做梦dreamed / dreamt，dreamed / dreamt feed喂fed，fedfeel触摸felt，feltfight作战fought，foughtfind找出found，foundflee (逃跑) fled fledget（得到）got gothang（吊死）hanged hangedhang（悬挂）hung hunghave / has有had，hadhear听到heard，heardhold（抓住）held heldkeep保持kept，keptlay (产卵) laid laidlead引导led，ledlearn学习learnt / learned，learnt / learned leave离开left，leftlend借贷lent，lentlight点着lit / lighted，lit / lightedlose遗失lost，lostmake制作made，mademean表…意思meant，meantmeet遇到met，metpay支付paid，paidprove证明proved，proved / provenquit放弃quit/quitted，quit / quittedrebuild改建rebuilt，rebuiltretell复述retold ,retoldsaw锯sawed ,sawed / sawnsay说said ,saidseek寻觅sought ,soughtsell卖sold ,soldsend送/寄sent ,sentsew缝合sewed ,sewn / sewedshine发光shone ,shone 擦亮shined ,shinedshoot放（炮）shot ,shotsink下沉sank / sunk，sunk / sunkensit坐sat，satsleep睡slept ,sleptsmell发出气味smelt ,smeltsow种植sowed ,sown / sowedspell拼写spelt / spelled ,spelt / spelledspend花费spent ,spentstand站立stood ,stoodsweep打扫swept ,sweptspit吐出spat / spit, spat / spitstick (粘贴/刺) stuck stuckteach教taught ,taughttell告诉told, toldthink思考thought ,thoughtunderstand了解understood ,understoodwet淋湿wet / wetted ,wet / wettedwin获胜won, won(5) ABC型（动词原形、过去式与过去分词三者不同形）arise出现arose，arisenawake醒来awoke，awaked / awokenbe(am / is / are)是was / were，beenbegin（开始）began begunbite咬bit，bittenblow吹blew，blownbreak打破broke，brokenchoose选择chose，chosendo / does做did，donedraw画，拉，拖drew，drawndrink（喝）drank drunkdrive驾驶drove，driveneat吃ate，eatenfall掉落fell，fallenfly飞flew，flownforbid禁止forbad，forbiddenforget忘记forgot，forgottenforgive原谅forgave forgivenfreeze结冰froze frozengive给gave，givengo去went，gonegrow成长grew，grownhide（躲藏）hid hiddenknow知道knew，knownlie躺lay，lainmistake误认mistook，mistakenmisunderstand误会misunderstood，misunderstoodride骑rode ,riddenring（铃响）rang rungrise上升rose, risensee看saw seenshake摇shook ,shakenshow显露showed，shownsing唱歌sang ,sungspeak说spoke ,spokenspring跳跃sprang / sprung ,sprungsteal偷stole ,stolenswim游泳swam ,swumtake拿took, takentear撕裂tore ,tornthrow投/扔threw, thrownwake醒着woke / waked ,waked / wokenwear穿着wore, wornwrite书写wrote, written动词原形中文意思过去式过去分词can 能 couldmay 可以 mightshall 将 shouldwill 将 would（５）现在分词（也可总结为规则以ie结尾改为y + ing）die（死）dying dyinglie（躺，平放，说谎）lying lyingtie（系,打结）tying tying。