All normally developing children possess the innate knowledge to attain full linguistic proficiency in their first language. In contrast, adults exhibit considerable variation in their ultimate attainment of second language proficiency. The Critical Period Hypothesis offers a plausible framework for explaining the disparities observed between first and second language acquisition. This hypothesis posits the existence of a finite developmental span during which the acquisition of a language to a native-like level is feasible; subsequent to this critical period, the capacity for language acquisition diminishes. Numerous scholars have dedicated their efforts to investigating the veracity of this critical period phenomenon. In light of its potential existence, this paper explores its implications for first language acquisition and its ramifications for second language acquisition. With a primary emphasis on the domain of second language acquisition, this study delves into the rationales underlying the assumption that humans may be subject to a critical period for language acquisition. Furthermore, it scrutinizes the extent to which the principles governing acquisition in a second language environment may or may not be applicable to the acquisition of a second language in a distinct foreign language environment.
