Medium of instruction

A medium of instruction (plural: usu. Mediums of instruction, but the archaic media of instruction is still used by some) is a language used in teaching. It may or may not be the official language of the country or territory. Where 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".