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Note: I'm not a linguist, and I realize I might be treading in a grey area here.

I'm wondering what the differences (and/or similarities) between native language, first language, mother tongue and L1 are. The first three, I find, are often used interchangeably in casual conversation. In academic linguistics though, are there generally accepted differences between these terms? Also, where does that leave L1? I believe it's an academic term, but I often see it defined relative to the other three casual terms.

A quick Google search seems to reveal there is a lot of confusion around these terms, and possibly no straightforward answer. It also doesn't help that the Wikipedia article groups the four terms into one article and has fewer citations than I would like. The only thing I've been able to gather is that the tendency seems to be for "native language" to mean proficient and for "first language" to mean chronologically first.

In particular, I'd like to find out (if possible) what term or terms are applicable to the following scenarios:

  • A chronologically first language with which the speaker is no longer fluent or even competent.
  • A language learned to fluency in adulthood (with or without a foreign accent - though I realize the latter is rare).
  • A language learned to fluency in childhood (within the critical period) that is not chronologically first.

I realize fluency might not be the best word to use...but the words I would normally use are the ones that I'm seeking clearer definitions for!

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I personally use L1, L2 etc., to avoid the NS (native speaker) vs NNS (non-native speaker) dichotomy and all ensuing unnecessary connotations. – Alex B. Feb 26 '14 at 1:53
One problem in answering your question is that there are also at least two different ways people use the terms "fluent" and "fluency"! For some it's the same as proficiency, for others it's being able to communicate fluidly, without pauses to think or interpret what was said and potentially lose the thread. You can be fluent and still have a strong accent, limited vocabulary, and make many textbook errors. – hippietrail Feb 26 '14 at 9:31
@hippietrail Yes, fluency was definitely not the best word. I'm looking for non-so-limited vocabulary, and little to no textbook errors. I guess proficiency would be the right word then? – DPenner1 Feb 27 '14 at 0:00
Terms "mother tongue" and "native language" can be politically charged. A friend from India insisted his "native language" was Kannada though admitted he learned it at age 6 (previously spoke just Hindi). Likewise, a girl from Ukraine claimed Ukrainian as her "mother tongue" though admitted she had grown up speaking Russian, (studied Ukrainian at college). Regionalism/nationalism was to blame in both cases. Better to ask what's the first language someone spoke or what they use mostly at home with family. – Joe Pineda Feb 28 '14 at 5:34
up vote 6 down vote accepted

OK, the fact of the matter is that everybody learns their own languages, in their own ways, in their own times, places, and circumstances. It is normal for kids to have several languages at home, and to pick up others as needed, by playing with other kids. Those languages either flourish through use, or wither and get forgotten by disuse, like any human skill.

Plus, people vary not only in their unique language experience, but in their skill at apprehending and using it. Also like any human skill. That's a vast amount of individual variation.

By contrast, labels like

Native language,
First language,
Mother tongue
.. etc.

are invented by people who need abbreviations for commonly-referenced groups of characteristics, usually characteristics that are common only in monolingual places like the USA, where almost everybody speaks only English, and often finds multilingualism threatening.

They are not terms defined in the Qur'an or the APA Style Manual; they are just abbreviations, which may be useful in certain contexts among certain kinds of professional. That's all, really.

These terms, and others, may or may not be applicable to the situations you mention. Or to others one can easily imagine. I repeat, they're just nonce forms, with localized definition and localized utility.

They are Not Ready For Prime Time, in other words, so you shouldn't take them too seriously. And they certainly don't cover every possibility.

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I wrote a blog post about this very topic last week, on the International Mother Language Day.

There is unfortunately no clear-cut answer if you speak more than one language. The different terms are used in different contexts and for varying purposes. For me 'mother tongue' and 'native language' are more or less interchangeable. The term 'first language' is as far as I understand not the chronologically first language, but the one a speaker is fluent in and feels most comfortable to speak. This means your 'first language' can change depending on where you live and which language you speak the most.

Your first question is intriguing and I also wrote about the scenario in my blog. If you no longer speak the language(s) you learnt as a child, based on the monolingual research terminology, you would be "mother-tongue-less" - however you would have a L1.

If you have become fluent in a language later in life, you have a 'native level fluency'. It's difficult to draw the line with regards to accents - different "native" speakers have vastly varying accents as well, so why would an accent from an other area prevent you from being called fluent?

If you have learnt a language as a child and you are fluent in it, it is one of your 'native languages' - the notion that there could only be one 'mother tongue' or 'native language' comes from a monolingual perspective and doesn't apply to bilingual people.

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Hi Rita, welcome and thanks for your contribution. I'm a little confused by your definition of L1 as language of highest proficiency, and not as the chronologically first languages. According to my experience, the overwhelming majority of SLA researchers use L1 in the sense of chronologically first language. – robert Feb 26 '14 at 16:57
Hi Robert, you are right, it should have said 'first language' not L1 in the third paragraph of my response. Through language attrition you can lose L1 and for example be a bilingual with two L2. – Rita Rosenback Feb 27 '14 at 11:14

In my opinion, none of the terms relate to the fluency of the language. The expression 'first language' relates to the vocabulary and linguistic variations (i.e. grammar, semantics) most commonly used by the speaker, which allows the person to practice a particular 'slang' to communicate within the environment they live in, even if they are not fluent using that particular language (in terms of 'academic' language).

Mother tongue/native language, however, involves a brain process - training, which starts when we are born and that includes components, elements and other types of communication (i.e. body language) that we adopt when we are little in order to survive within the context, and that create an specific mental structure - code that will dictate our future languages acquisition.

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Hi Cecilia, welcome and thanks for your answer. Do you have any sources for these definitions? They seem to contradict current thinking in research on Second Language Acquisition, but I would be happy to take a look at any alternative definitions, if there are sources. – robert Feb 27 '14 at 10:11
Hi Robert, thanks for your reply. New studies have found that the brain tends to use the mother tongue's linguistic structure as a foundation for the second language acquisition. Speakers of a second language tend to accommodate their L2 to the rules of their tongue of origin. I will look out for the sources. – Cecilia Feb 27 '14 at 11:24

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