A person's second language or L2 is a language that is not the native language of the speaker, but that is used in the locale of that person. In contrast, a foreign language is a language that is learned in an area where that language has no presence or is not commonly spoken by the community as a whole. Some languages, often called auxiliary languages, one of them being English, are used primarily as second languages. More informally, a second language can be said to be any language learned in addition to one's native language, especially in the context of second-language acquisition (that is, learning a new foreign language).
A person's first language is not necessarily their dominant language, the one they use most or are most comfortable with. For example, the Canadian census defines first language for its purposes as "the first language learned in childhood and still spoken", recognizing that for some, the earliest language may be lost, a process known as language attrition. This can happen when young children move, with or without their family (because of immigration or international adoption), to a new language environment.
A foreign language is a language originally from another country. It is also a language not spoken in the native country of the person referred to, i.e., an English speaker living in Spain can say that Spanish is a foreign language to him or her. These two characterisations do not exhaust the possible definitions, however, and the label is occasionally applied in ways that are variously misleading or factually inaccurate.
Some children learn more than one language from birth or from a very young age: they are bilingual or multilingual. These children can be said to have two, three or more mother tongues: neither language is foreign to that child, even if one language is a foreign language for the vast majority of people in the child's birth country. For example, a child learning English from his English father and Irish at school in Ireland can speak both English and Irish, but neither is a foreign language to him. This is common in countries such as India, South Africa, or Canada due to these countries having multiple official languages.
In general, it is believed that children have advantage to learning a foreign language over adults. However, there are studies which have shown adult students are better at foreign language learning than child students. It is because adults have pre-existing knowledge of how grammar works,and a superior ability of memorizing vocabulary.
