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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.