Mother language?

[Torsten]

So it's all about mothers and languages I guess. You see, there is this term "native language" which is quite widely used. Your native language is the language you learned as child, at least in most cases. It's your first language, your mother tongue. In an earlier thread we established that mother tongue and native language are more or less synonyms with the latter probably being more popular.

But there obviously is also the term "mother language". At least that's what mother Google tells us. So, my question is what is a "mother language" and what is the difference between your "native language" and your "mother language"?
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[Mister Micawber]

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I've never heard mother language myself. I presume it is a less common synonym for mother tongue.

An excerpt from a reputable on-line use--- which source is also most of the hits on the first 3 Google pages:

'International Mother Language Day was proclaimed by UNESCO's General Conference in November 1999.... All moves to promote the dissemination of mother tongues will serve not only to encourage linguistic diversity and multilingual education but also to develop fuller awareness of linguistic and cultural traditions throughout the world and to inspire solidarity based on understanding, tolerance and dialogue....'
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