English as a second language (ESL), English for speakers of other languages (ESOL), English as an additional language (EAL), and English as a foreign language (EFL) all refer to the use or study of English by speakers with different native languages. The precise usage, including the different use of the terms ESL and ESOL in different countries, is described below. These terms are most commonly used in relation to teaching and learning English, but they may also be used in relation to demographic information. English language teaching (ELT) is a widely used teacher-centred term, as in the English language teaching divisions of large publishing houses, ELT training, etc.
Contributions by Gailtb, BrainyBabe, and Andycjp.