Accuracy refers to how correct learners' use of the language system is, including their use of grammar, pronunciation and vocabulary.

An achievement test evaluates a learner's understanding of a specific course or study programme.

Acquisition is the way we learn our first language, i.e. through being involved in real communication, and without formal teaching.

Action research is a development tool for a teacher that involves observing or gathering other data about a class through interviews, case studies, and questionnaires.

An adverbial clause tells us more about a main clause, in the same way as an adverb tells us more about a verb.

Affective factors are emotional factors which influence learning. They can have a negative or positive effect.

Affective strategies are learning strategies concerned with managing emotions, both negative and positive.

Affixes are groups of letters that are added to the beginning or the end of words to make new words.

Affricates are consonant sounds made up of a stop, like /t/, immediately followed by a fricative, like /s/.