What is a first language?

The linguistic concept, first language, has for long had conflicting opinions as to what constitutes its definition. This article will do a concise breakdown of the meaning of first language. First language (L1), also known as mother tongue (MT), is the language a person acquires at a very young age. It is the language acquired from birth and also the first language from which a person obtains their ability to communicate—a medium of communication.  

It is acquired from one's immediate environment, usually from parents, older siblings, relatives, etc. First language is the language a person first acquires a means of expression in, and this language is acquired from the ages of 7 months to 12 years. A person gets instilled with the values, norms and culture of the language which to an extent, shapes their identity.

It is as Michael Halliday puts it, acquired by imitation. A child acquires their first language by imitating the sounds produced in their immediate environments. From imitating these sounds as they are produced by persons in their immediate environments like parents, relatives, neighbors, the child starts to learn how those sounds are paired. This is an advanced stage where the child no longer has to depend on oddly pronouncing sounds they hear in there environment, but the child learns how they are paired to form meaningful expressions for ease of communication and self expression. This is particularly why it is the first language of expression.

However, contrary to what many believe, the first language of a person may not necessarily be their mother tongue or native language. A mother tongue (MT), or native language is the language of a speaker's parents, the language of a speaker's ancestors spoken by a group of people who form an ethnic group in a speech community, sharing norms, beliefs, and traditions that guide their way of life and how they relate with the outside world—as well as what constitutes their identity, and what forms their world view. 

A person's first language may not be their mother tongue for one major reason: it may not be the first language a child is exposed to. Recall the definition in the preceding paragraphs? A first language has to be the language a child is exposed to first in their immediate environment. So what this opines is that a child is not limited to their native tongue in terms of acquiring a first language, but the first language they are exposed to is what forms their first language.

For example; A child born in the United Kingdom by Nigerian parents will grow up to speak the English language as their first language. Simply because it is the language of the child's immediate environment, and the first set of people the child encounters will definitely make use of the language. 

See also: Language acquisition vs Language learning 

While a child born in Nigeria by Nigerian parents would acquire Nigerian languages such as: Igbo, Yoruba, Hausa, Efik, Tiv, Urhobo, to mention a few based on the region in which the child is raised.

So, first language may or may not be the mother tongue or native tongue of a person, but it must be the first language a child acquires from their immediate environment through imitation of sounds and relation with people in their immediate environments like their parents, relatives, neighbors, etc.

See also: Differences between a national language and an official language