L2: This is a short term referring to second language. In most cases the first language is referred to as the L1 while the second language L2. 2. Critical period hypothesis: This is a period where one is believed to have full potential of achieving native state fluency in a second language provided he gets the required exposure to that language. This period starts when one is two years and runs through to the end of puberty. 3. Foreign language: This is a language belonging to another country or region but practiced or learned by natives of another country or region. 4. Age differences: These are the inborn natural differences among individuals resulting from their difference in age. 5. L2 motivation: This is the inborn or self-motivation to learn a language. 6. Native state fluency: This is the level of language fluency where one is equated to the natives of a language even though it is a second language to him or her. 7. Lexical structures: The lexical structures of a language refer to the semantics morphology and grammar of a language. 8. Language acquisition: It is the process of learning a language from the time of onset to completion.