,because, as, since, for,表原因的用法区别,because （因为）的用法： 通常表示直接而明确的原因和理由，语气很强，用来回答why的问题, 多放于主句之后。 例：因为天气太冷，我们不能外出。 We couldnt go out because it was too cold.,as: “因为、由于”，语气比because弱，表示的是不言而喻、显而易见的原因和理由，其从句一般放在主句前. 如:由于时间很晚了，我们很快就回来. As it was late ， we came back soon. 因为下过雨，空气比较清爽。 As rain has fallen, the air is cooler.,since: “既然”, 语气较弱，强调已知的事实，其从句一般放在主句前。 既然你回答不出这个问题，我就问别人了。 Since you cant answer the question, Ill ask someone else. 既然他的方法不行，我们就试试你的吧. Since his method doesnt work, lets try yours. 既然你对此如此有把握，他会相信你的。 Since you are so sure of it， he”ll believe you.,for：并列连词，表示对前一分句补充说明，放在句末。 例：一定是清晨了，因为鸟儿在叫。 It must be morning for the birds are singing. 要下雨了，因为天气越来越暗了。 It will rain, for its getting dark。,原因状语从句 (Adverbial Clause of Cause),1. because since as for的用法区别,He introduced me because I was new. Since you are going, I will go, too. As it is raining, youd better take a taxi. It must have rained last night, for the ground is wet.,