1.引言儿童学习母语,在潜移默化中学会了讲话,掌握了母语的规则,并逐渐能理解成年人讲话的含义。语言学家把这个过程通常称为“语言习得”(language acquisition)。而第二语言或外语学习由于没有母语的学习环境,不能受周围人群的影响而掌握,必须通过正式的语言教学才能学会,这就是第二语言习得 1. Introduction Children learn a mother tongue, learn to speak in a subtle way, master the rules of mother tongue, and gradually understand the meaning of adult speech. Linguists commonly refer to this process as “language acquisition.” The second language or foreign language learning because there is no mother tongue learning environment, can not be affected by the influence of the surrounding population and must be formal language teaching to learn, this is the second language acquisition