①
since既然,因?yàn)?側(cè)重主句,從句表示顯然的或已知的理由.
Since you ask,I will tell you.你既然問,我就告訴你.
because因?yàn)?；表直接原?回答why的提問；一般放主句之后,也可單獨(dú)存在：We stayed at home because it rained.因?yàn)橄掠晡覀兇粼诩依?
②
although和while兩個連詞都可以用來引導(dǎo)讓步狀語從句,表示“雖然”、“盡管”之意,但表達(dá)的意思和用法卻不盡相同.
一、一般情況下,while在表示讓步語義時(shí)與although同義,兩者可以互用.
1.它們引導(dǎo)的讓步狀語從句都表示與主句中的某一動作或狀態(tài)有著意義上的對比.如：
(1) While this is true of some,it is not true of all.雖有一部分是真的,但不見得全都是真 的.
(2) While I feel great sympathy for you,I can’t really do very much to help.雖然我對你深為同情,但我實(shí)在是幫不上什么忙.
(3) They are generous although they are poor.他們雖然貧窮卻很大方.
(4) Although I appreciate her reasoning,I reject her conclusions.雖然我欣賞她的推理能力,卻不能接受她的推論.
2.while和although引導(dǎo)的讓步狀語從句都不能和but連用,但可以跟nevertheless或yet連用.如：
(1) While I admit I did it,(nevertheless) I didn’t mean to.盡管我承認(rèn)干了這件事,但我并不是故意的.
(2)Although admission was free,(nevertheless)few people attended the lecture.盡管免費(fèi)入場,但幾乎沒什么人去聽演講.
(3)Although (he was) seriously wounded,(yet) he refused to leave the battle line.他雖然身負(fù)重傷,但堅(jiān)持不下火線.
它們引導(dǎo)的讓步狀語從句都可以省略與主句相同的主語和與其相應(yīng)的be動詞.如：
(4) While (I am)told you are wrong,I am sure you are honest.盡管我知道你錯了,但我還是相信你很誠實(shí).
(5) Although (she was) not yet six months old,she was able to walk without support.她雖然還不到6個月,但已能不用攙扶走路了.
二、在一些特定的語境和語體中,這兩個詞在用法上還是有細(xì)微差別的.
1.while引導(dǎo)的狀語從句在大多數(shù)情況下置于句首；而although引導(dǎo)狀語從句,可置于句首也可置于句中或句末.如：
(1) While we don’t agree,we continue to be good friends.盡管我們意見不一致,但我們?nèi)允呛门笥?
(2) While the ways used are quite different,the result is similar.雖然所用方法完全不同,但效果卻相似.
(3) Although young Tom comes of a musical family,he doesn’t like singing.雖然年輕的湯姆出身于音樂之家,但他不喜歡唱歌.
(4) We’ll try to finish the work in time although we are short of hands.雖然缺少人手,我們還是要按時(shí)完成這項(xiàng)工作.
(5) Common salt,although (it is) dissolved in water,does not change its chemical properties.盡管食鹽溶于水,但其化學(xué)性質(zhì)不變.
2.although引導(dǎo)的狀語從句常含常有“not”一詞,修飾主句或糾正一個錯誤的概念；而while一般不這樣用.如：
(1)I have a lot of my grandfather’s features although I’m not so tall as he was.雖然我不及我祖父個子高,但相貌卻與他很相似.
(2) In any case,he was very lovable although not at all tidy.總之,他還是挺招人喜歡的,盡管一點(diǎn)也不整潔.
3.although...but不可連用,但but although可以連用,且往往置于句首；而while沒有這種用法.如:
(1) But although the situation was clearlydang-erous,the public was not at all happy with the idea of a government police force.盡管局勢是明顯地危險(xiǎn),可是老百姓對政府動用警力的做法仍很不滿意.
4.while引導(dǎo)的讓步狀語從句在意義上一般與主句的對比不太強(qiáng)烈,即主句與從句只是部分不一致；而although在表示讓步語義時(shí)是最為通用的從屬連詞,所引導(dǎo)的從句往往使主句內(nèi)容含有似乎使人感到意外或料想不到之意.以下例句中while和although不可換用.
(1) While I admit his good points,I can see his shortcomings.盡管我承認(rèn)他的優(yōu)點(diǎn),我也能看到他的缺點(diǎn).
(2) While I like the color of the hat,I don’t like its shape.雖然我喜歡這頂帽子的顏色,但不喜歡這種式樣.
(3) Although my car is very old,it still runs very well.雖然我的汽車很舊了,但跑起來挺不錯.
(4) He brought me a cup of coffee although I had asked for tea.雖然我要的是茶,他卻給我端來一杯咖啡.
(5) Smith kept her coat on although it was warm in the room.盡管房間里很暖和,可史密斯仍舊穿著外套.
5.這兩個連詞都可用于讓步結(jié)構(gòu),但兩者所連接的句子的主從關(guān)系恰好相反.比較：
(1) Although it looks like a huge monster,that country is in fact a paper tiger.雖然看起來那個國家像個龐然大物,但實(shí)際上是一只紙老虎.
(2) While it is in fact a paper tiger,that country looks like a huge monster.盡管那個國家實(shí)際上是一只紙老虎,但看起來像個龐然大物.