SOME KEY TERMS
L1 refers to the language acquired or learned first by the student. It generally refers to the mother tongue or the first language of the student. Mother tongue is a fuzzy concept.
The term first language focuses upon the serial order in which a language may be acquired or learned. It is possible that a child may acquire or learn two or more languages simultaneously. Under such circumstances, it is possible for a child to have more than one language as her first language or her mother tongue. (See Simultaneous Acquisition of Two Languages: An Overview by Shyamala Chengappa and M. S. Thirumalai, published by the Central Institute of Indian Languages, Mysore, India, 1986.)
L2 refers to the language or languages acquired or learned subsequent to the first language. The term Second Language also refers to the language or languages acquired or learned subsequent to the first language. It is generally assumed that the first language of a person comes to influence the quality of learning and use of the second language. In this context, the term Source Language generally refers to the first language or the mother tongue or L1 and the term Target Language refers to the second language or L2.
The term Foreign language refers to that language for the use of which there is no immediate reinforcement outside the classroom. For example, if English is learned by a Japanese student from Japan in the United States, the status of such learning is treated as second language learning, because he has abundant opportunities to use that language outside his classroom. On the other hand, if the same student learns English in his country, he may not have equally abundant opportunity to use English outside his classroom. Under this condition, the student is deemed to be learning English as a foreign language. It is important that we keep this distinction in mind when we teach English to speakers of other languages, because each teaching/learning situation will require different materials, strategies, and goals.