A person’s second language or L2, is a language that is not the mother tongue 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 is not generally spoken. Some languages, often called auxiliary languages, are used primarily as second languages or lingua francas. More informally, a second language can be said to be any language learned in addition to one’s mother tongue, especially in 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.