A second language is a language that is learned in addition to a person's mother tongue, or first language. “Second” can refer to any language that is learned subsequent to the mother tongue, thus it can also refer to the learning of a third or fourth language. Second language may be acquired by absorption because it is spoken in the home, or actively pursued by taking courses. The more the second language differs from a person's mother tongue in terms of alphabet and grammar, the more difficult it will be to learn.