The discussion of language critical period suffers from the lack of a commonly accepted definition of language. Some aspects of language, such as phoneme tuning, grammar processing, articulation control, and vocabulary acquisition can be significantly improved by training at any age and therefore have weak critical periods. Other aspects of language, such as Prefrontal Synthesis, have strong critical periods and cannot be acquired after the end of the critical period. Consequently, when language is discussed in general, without dissection into components, arguments can be constructed both in favor and against the strong critical period of L1 acquisition.