In Teaching English to Speakers of Other Languages (TESOL), English is taught to individuals including immigrants or refugees who now reside in English-speaking countries, such as the United States, or to people raised in non-English-speaking countries or environments.

Theories
There are many current TESOL theories, most of which relate to teaching and learning. TESOL learning theories refer to English language acquisition techniques and difficulties, while TESOL teaching theories focus on different teaching methods employed by teachers and their expected results.

Interference
One illustrative TESOL learning theory is the idea of language interference. A non-native English speaker may suffer from "interference" by his mother tongue while learning English. This may take such forms as projecting his native tongue's grammatical patterns onto English grammatical patterns, having difficulty learning a new alphabet, or unconsciously retaining the mother tongue's pronunciation for certain letters and words.

Direct Approach
One example of a TESOL teaching theory is the direct approach. Teachers may use it alone or in combination with other theories and techniques. The direct approach builds on inductive learning and consists of teaching and communicating in the classroom solely in English (although sometimes with the help of pictures or pantomime), but without the aid of grammar explanations.