Mother tongue and Natural language

Mother tongue noun - One's native language; the language learned by children and passed from one generation to the next.

Natural language and mother tongue are semantically related. In some cases you can use "Natural language" instead a noun phrase "Mother tongue".

Natural language noun - A human written or spoken language used by a community; opposed to e.g. a computer language.

Mother tongue and natural language are semantically related. You can use "Mother tongue" instead a noun phrase "Natural language".