Key English Test -  a Cambridge English examination for students at A2 level.

See KET.

First language - also referred to as primary language, native language and mother tongue.

Second Language. It is any language that a person knows aside from his/her first language.

See second language acquisition.

Language Acquisition Device - see innatist theory.

Grading your language means using language appropriate to your students' level. When you are explaining a new word or phrase, it is easy to accidentally use another piece of unfamiliar vocabulary. You then need to explain that, and in doing so you might introduce a third unfamiliar term! Instead, you should try to explain the vocabulary item without using other words or grammatical structures that the students don't already know.

See warmer.

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A learning platform is any online information system used for teaching. This maybe for exclusively online courses, such as this one, or to support traditional teaching in schools, universities, etc.