Is "mother tongue" exactly the same as "native language"?

Solution 1:

"Mother tongue" and "native language" are set phrases that both refer to the language one has started learning from birth. One generally associates "mother" with "tongue" and "native" with "language" but it is sometimes found the other way round. "Language" and "tongue" are here synonyms.

I would say "mother" or "native" is not identical though. When using "native" the reference is more to the country/nation. When using "mother" the reference is to the parent (mother or father), which gives it a warmth and personal relationship that the word "native" doesn't have.

I've found a sentence that I think can explain what I mean about "native" and "mother" although native being used here in association with country:

As a parent living far from my native country I have often experienced the fear that my children would not learn their mother language well.

In this whole text the use of "mother tongue" is not identical and I doubt the person who wrote it would have used "native language" (or "native tongue") where she used "mother language".

Solution 2:

Multilingualism adds a questionable level of complexity to the established equations.If we were to define the terms based on today's demography then it sure is relevant to consider the following. And FYKI monolingualism is a thing of the past.

Wiki states:

"One can have two or more native languages, thus being a native bilingual or indeed multilingual. The order in which these languages are learned is not necessarily the order of proficiency. For instance, a French-speaking couple might have a daughter who learned French first, then English; but if she were to grow up in an English-speaking country, she would likely be most proficient in English."

Wiki defines the concerned terms by establishing a differential approach.

Defining mother tongue:

Based on origin: the language(s) one learned first (the language(s) in which one has
established the first long-lasting verbal contacts).
Based on internal identification: the language(s) one identifies with/as a speaker
of;
Based on external identification: the language(s) one is identified with/as a
speaker of, by others.
Based on competence: the language(s) one knows best.
Based on function: the language(s) one uses most.

A native speaker is defined according to the guidelines that:

The individual acquired the language in early childhood
The individual has intuitive knowledge of the language
The individual is able to produce fluent, spontaneous discourse
The individual is competent in communication
The individual identifies with or is identified by a language community
The individual does not have a foreign accent