because, since, as, for, 这几个词都是表示“原因”的连词，语气由强至弱依次为：because since as for 其中because, since, as 均为从属连词，引导原因状语从句；而for 是并列连词，引导并列句。 1. because 表示直接原因，其语气最强。 常用来回答why 的提问I stayed at home because it rained. Why is she absent? Because she is sick. 在强调句型中，只能用because It was because I missed the early bus that I was late for school. 要点：不要把连接词 because 与介词短语because of ( + 名词或-ing 形式) 相混淆；He lay in bed because he had caught a bad cold. He lay in bed because of a bad cold.since 表示显然的或已为人所知的理由， 常译为“因为”、“既然”，通常置
