A medium of instruction (plural: media of instruction, or mediums of instruction) is a language used in teaching. It may or may not be the official language of the country or territory. If the first language of students is different from the official language, it may be used as the medium of instruction for part or all of schooling. Bilingual or multilingual education may involve the use of more than one language of instruction. UNESCO considers that "providing education in a child's mother tongue is indeed a critical issue". In post secondary, university and special educational program settings, content may often be taught in a language that is not spoken in the students' homes. This is referred to as content based learning or content and language integrated learning (CLIL). In situations