Language immersion, or simply immersion, is a method of teaching a second language in which the learners’ second language (L2) is the medium of classroom instruction. Through this method, learners study school subjects, such as math, science, and social studies, in their L2. The main purpose of this method is to foster bilingualism, in other words, to develop learners' communicative competence or language proficiency in their L2 in addition to their first or native language (L1). Additional goals are the cognitive advantages to bilingualism.
In complete immersion, almost 100% of class time is spent in the foreign language. Subject matter taught in foreign language and language learning per se is incorporated as necessary throughout the curriculum. The goals are to become functionally proficient in the foreign language, to master subject content taught in the foreign languages, and to acquire an understanding of and appreciation for other cultures. This type of program is usually sequential, cumulative, continuous, proficiency-oriented, and part of an integrated grade school sequence. Even after this type of program, the language of the curriculum may revert to the first language of the learners after several years.