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A first lan­guage (also native lan­guage, moth­er tongue, arte­r­i­al lan­guage, or L1) is the language(s) a per­son has learned from birth or with­in the crit­i­cal peri­od, or that a per­son speaks the best and so is often the basis for soci­olin­guis­tic iden­ti­ty . In some coun­tries, the terms native lan­guage or moth­er tongue refer to the lan­guage of one’s eth­nic group rather than one’s first lan­guage. Chil­dren brought up speak­ing more than one lan­guage can have more than one native lan­guage, and be bilin­gual. By con­trast, a sec­ond lan­guage is any lan­guage that one speaks oth­er than one’s first language.