What is the difference between First Language and Second Language? (in 5 lucid dimensions) Decoding Definitions Miniseries: Tackling Question #1

What is the difference between First Language and Second Language? (in 5 lucid dimensions) Decoding Definitions Miniseries: Tackling Question #1

This article answers Q1 of the Miniseries “Decoding Definitions” on LEA “What is the difference between First Language and Second Language?” from 5 dimensions.

Difference between first language and second language

In the course of our professional work, we usually come across many specialised terms from theoretical and applied linguistics which we used with assumed universal understanding. In actual fact, some of these terms can be controversial and linguists might mean different things as they use them in different contexts. In fact, laypersons and academics may use them in completely different ways.

The current Miniseries “Decoding Definitions” attempts as much as possible to disambiguate some of these competing terms for language educators. Notwithstanding such, do note that the exact definition adopted by any linguist or researcher may depend on the ideological perspective(s) of the user, purpose or methodology of his/her research, time and context where the definition is used, etc. Many definitions remain heavily contested, despite the apparent common use. Therefore, I aim to represent these concepts as broadly and descriptively as possible, instead of prescriptively adopting a stand. These terms will be captured in the glossary on this website eventually. And I hope these articles will help you in your professional journey!

Key differences between first language and second language in 5 dimensions

For our first article in these series, I will attempt to provide a comprehensive answer pertaining to definition in the question: What is the difference between First Language and Second Language?

I will address this question by considering possible definitions which distinguish both in 5 lucid dimensions: 

  • Acquisition context
  • Sequence
  • Proficiency level
  • Frequency of use
  • Positioning in education
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1. Defining by acquisition context

acquisition context
Photo from Envato Elements / A couple holding a newborn baby while talking to it

The most classic dimension in which the difference between first language and second language is established is the acquisition context. When a researcher uses the term “first language”, it usually refers to the language that typically emerges in the sphere of birth to early childhood (or “native language” as the individual is born into it), acquired by the individual without any formal instruction. As such, it is the language of the home and/or community, especially one which is used by the assumed primary caregiver – the mother – and is also usually referred to as the “mother tongue”.

First language acquisition largely occurs through a natural and unplanned process, often taking place within unstructured environments like homes, playgrounds or other such informal settings. Interactions with family members, peers, and various other communication partners contribute significantly to this language development, where young children unconsciously develop L1 linguistic competence through mere exposure – in most typical situations.

Contrarily, the second language is usually acquired through a more structured and planned methods brought forth within a varied age range. In other words, it is any additional language that an individual acquire after his/her first language has been acquired. While some individuals may commence their second language learning journey during childhood (e.g. primary 1 onwards), others may only learn a new language well into their adolescence or adult years.

This delayed initiation ordinarily exposes learners to L2 later in life, often as a necessity or desire, rather than being a natural, involuntary consequence of their environment. Moreover, this acquisition frequently transpires within structured educational settings, such as schools, language centres, or universities that rely on curricula, teachers, textbooks, and other systematic resources.

Despite the distinctions between the acquisition contexts of first and second languages, one must acknowledge the inherent complexity and intertwining of these two processes. While it is true that the learning of an L1 tends to occur in early childhood within unplanned settings, many individuals are concurrently exposed to multiple languages during this developmental stage, resulting in simultaneous acquisition or successive acquisition of more than one language. In such a sense, these early bilinguals/multilinguals can be described to have possessed more than one first language (e.g. 2 or 3 L1s). This can be a very common phenomenon, if not already the norm, in regions with high degrees of societal bilingualism/multilingualism (e.g. Europe, Singapore, Malaysia, Quebec). 

Conversely for the L2 contexts, there is a growing trend of incorporating more naturalistic and communicative approaches within L2 curricula, intentioned to foster an environment that better approximates the learning conditions associated with an L1. Language teaching approaches and methods such as the Natural Approach or the Total Physical Response tend to emulate the L1 acquisition process within L2 learning situations.

2. Defining by sequence

Newton cradle with balancing pendulum of silver metal balls
Photo from Envato Elements / Balls laid in sequence within a Newton’s Cradle

I must put in a very strong disclaimer that academia hardly engages the terms “first language” and “second language” purely by the sequence of acquisition, although this elephant in the room has to be addressed. Otherwise, why are they termed as such?

Studies in bilingualism and second language acquisition have arguably been around for centuries (iffy claims that are hard to substantiate). However, the more established systematic development of the field occupying a substantial position within language sciences was really very much a phenomenon since the 1960s from academia in monolingual anglophone areas.

Monolingualism was deemed the norm (monolingualism in English for these areas) such that everyone only speaks a language. Those who spoke more than one, were then those anomalies that possess a second language. To distinguish such languages within individuals for the sake of policymaking and research, the terms “first language” and “second language” were then required. Regrettably, I have not really found any sources which reliably explains clearly the assumptions behind the coining of both terms (e.g. why not use “additional language”).

Irregardless, “first language” (L1) has come to denote the earlier acquired language as mentioned in the previous section while “second language” (L2) comes after in sequence. But, things got complicated. As L1 and L2 were further characterised and distinguished from one another, we realise that the languages within the repertoire of early bilinguals (e.g. children exposed to and able to use more than one language proficiently) would not be easily categorised in sequence.

Eventually, researchers come to agree that “L1” will come to denote all the languages acquired during early childhood (e.g. age range is also argued), regardless of simultaneous or successive. For monolinguals, it will remain as only one L1; for bilinguals/multilinguals, it will be more than one.

So, what about L2? While it used to mean the additional language that is acquired after the L1 based on largely monolingual perception (which seems to frame bilingualism like a black swan occurrence), the scoping in definition has also widened. Any additional language(s) that is acquired after the L1(s) has been established (i.e. after early childhood) are considered L2(s). For instance, an early bilingual who has already 2 L1s, English and Mandarin, in his/her repertoire comes to learn another 2 additional languages in adulthood, Hindi and German, will then be recognised to have acquired both Hindi and German as L2s. In other words, for polyglots who can speak multiple languages effectively, the group of languages that are acquired during early childhood are regarded L1s and those after early childhood are all L2s. 

You must be wondering: is it just convenience for all L2s to be grouped together? Well, that will probably not be a scientific way to do things. The scientific assumption (I conceive that it can be challenged nevertheless – and it has indeed been challenged) is that acquisition mechanisms (e.g. processes, challenges) of any additional language(s) after the L1s have been established are very much similar. Accordingly, it makes little professional sense to identify L3, L4, L5, etc; and that L2(s) all the way to infinity should suffice for scientific study.

Notwithstanding such, there are indeed scholars who distinguish third and/or additional language(s) from L2 with the pursuit to account for specific characteristics unique to the acquisition of additional language(s) beyond the second. Moving even further, the use of translanguaging as a theory of language in recent years may also radically reframe how additional languages are appropriated into the system. We may encounter a very different framing of L1s and L2s in future, for all we know.

3. Defining by proficiency level

business persons engaging in communication
Photo from Envato Elements / Business persons engaged in mobile communication

With the conditions set by the 2 earlier dimensions, the effects become manifested in the 3rd dimension: proficiency level. L1 proficiency entails a strong linguistic foundation and an innate understanding of the language, as it is the primary means by which individuals engage in routine communication, cognitive processing, and cultural participation. Consequently, L1 proficiency is often characterised by high levels of communicative competence, built upon an inherent familiarity with linguistic rules, structures, and patterns.

In contrast, L2 proficiency often mirrors a more diverse spectrum of competencies, as it can range from minimal conversational abilities to near-native fluency, contingent on various factors including age, motivation, intensity of exposure, and instructional methods. There are, of course, a proportion of L2 learners who have attained expert proficiency and are indistinguishable from L1 users (or sometimes better known as the native speakers of that L2). The hard truth is that majority of L2 learners hardly attain that kind of performance in general to be recognised or assessed as so.

As such, when life experiences change such that individuals experience L1 attrition to the extent that they are unable to perform at the proficiency expected of L1 users; accompanied with the reality that their later acquired L2(s) become more proficient, dissonance can occur on the definition of L1(s) and L2(s) for these individuals.

Undoubtedly, depending on contexts, we can maintain the definition using the two earlier dimensions of acquisition context and sequence which is the case for most research studies. However, another definition adopted for “first language” that distinguishes it from the innateness implied in the earlier dimensions is that it can also refer to the language in which an individual is highly proficient and feels most comfortable using, especially in contrast to one’s “second languages”. Of course, such a definition is usually only employed by adult bilinguals/multilinguals or research studies working with them.

For instance, in bilingual/multilingual societies with a dominant language (usually the lingua franca which is the medium of administration and education), individuals with varying L1(s) which are not the dominant language will usually experience attrition (and also incomplete acquisition) after extended periods of formal schooling while they gain high proficiency in the dominant language (initially their L2 based on earlier definitions). Thereafter, they may thus either recognise both their earlier L1 and the latter L2 as L1s; or the dominant language as L1 with the attrited L1 as L2. This is usually found in expressions like “I was born into a family using Mandarin as L1, but now I am using English as my L1 and my Mandarin as my L2”.

4. Defining by frequency of use

frequency of use in different contexts
Photo from Envato Elements / Language use in a variety of contexts

Somewhat related to the earlier dimension is the degree of dominance. A subset definition of language dominance in an individual is the relative proficiency of the various languages the individual has in his/her repertoire – pretty much the dimension we were discussing in the previous section.

The other subset, however, relates to the frequency of use across domains. The more frequently an individual uses a language in favour of others, the more it is like the L1 as demonstrated in the example ending the previous section: “I was born into a family using Mandarin as L1, but now I am using English as my L1 and my Mandarin as my L2”.

It is critical to appreciate that frequency of use generally correlates with proficiency in a language. The more an individual practises speaking, listening, reading, and writing in a language, the greater their knowledge of the language’s grammar, vocabulary, and culture; and their confidence in using the language.

In this regard, the L1(s) tend to be more frequently used, as individuals typically demonstrate greater proficiency, confidence, and cultural understandings in these languages compared to their L2(s). Notably, L1(s) are often associated with a sense of identity and belonging, as they are acquired through early childhood and familial interactions; as such, there is usually a strong emotional connection to one’s L1(s).

However, frequency is also largely governed by societal factors, as an individual may be driven to employ their L1 or L2 to a greater or lesser extent based on the cultural, economic, or social environments in which they find themselves. For example, while an individual may predominantly use their L1 in personal contexts, or informal communicative environments, their L2 may become more prevalent in professional or educational settings. The L2 can provide access to new resources, opportunities, and domains of communication, thereby increasing the frequency of use and leading to enhanced proficiency, confidence, and integration into the broader society.

In some cases, frequency of use can increase in favour for the L2 at the expense of the L1, particularly for individuals who have migrated to a context where their L2 becomes the primary language of communication; or that the L2 is the main lingua franca in the country of residence. Over time, as the individual becomes more immersed in the L2, the frequency of use of the L1 may decrease, leading to L1 attrition and the possible disconnection from their original cultural context and identity. Conversely, the L2’s importance may elevate in their life, as it facilitates social integration, economic success, and participation in various domains.

In such situations, the boundaries may become fuzzy. The use of the term “L1” may not necessarily always refer to the language acquired in early childhood, but may also refer to the L2 that has gained dominance in terms of frequency; while the language acquired in early childhood may still be regarded L1 or sometimes be considered the L2 (the sense of “using it as a L2” like in the previous section). Of course, similar to the previous dimension, should the definition of L1 and L2 is adopted based on the dimension of frequency of use, it is usually employed by adult bilinguals/multilinguals or research studies working with them.

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5. Defining by positioning in education

young learners engaged in a classroom
Photo from Envato Elements / Young learners engaged in a formal classroom

In the context of the education system, the definition may not be as clear cut whether it is part of the institutional nomenclature (e.g. L1 learning, L2 subjects) or found within educational research. If the definition is constrained from the perspectives of individuals (e.g. students learning a target language as a L2), then we can still largely assume that the definition of L1 and L2 is largely contextualised within the dimensions of acquisition context and sequence; or may be engaged with proficiency level and frequency of use for adult learners.

However, the definition of L1 and L2 can also take the perspectives of societal assumptions or the national narrative shaped by socio-political forces. For instance, L1 within an education system can refer to the medium of instruction (usually an official language or the de facto national language) that is employed across the board for all content subjects while L2 is used to denote all language subjects that are not that L1. In such situations, students offering the L2 as a subject may actually be speaking that target language as a L1 (e.g. ethnic Chinese students offering Mandarin as a “Languages Other than English” in Australia).

For such situations, the L1 serves as a powerful emblem of national identity within the education system of the given nation-state. It is institutionalised as a reflection of cultural heritage and plays a pivotal role in shaping the collective identity of the country and its citizens. The L2s are generally present in the system for selective bilingualism/multilingualism with factors associated with regional identity and economic demands.

The distinctions drawn between L1 and L2 within an educational system can have a significant impact on the approaches undertaken by respective educational systems to drive instruction. Recognising these distinctions as delineated within a system in relation to the definition across other dimensions for the individuals can lead to better decision-making on responsive pedagogies for our learners from varied linguistic backgrounds. 


We have combed through the different dimensions that may present differences between first language and second language for the purpose of definition. I hope I have provide further clarity to enable a more literate appreciation of the usage of these terms in policy and research. Moving forward, do keep your lookout on more question within this Miniseries. Maybe further down the pipeline, I might also provide infographics for easier digestion. Let me know if this is something you look forward to!

Thank you for reading! If you like what you are reading, do subscribe to our mailing list to receive updated resources and tips for language educators. Please also feel free to provide us any feedback or suggestions on content that you would like covered.


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