The language that is the target to be learned is referred to as L2, and the acquisition; the second language acquisition is known as the L2A, or much better known as SLA.
Formal instruction possesses a profound effect in the everyday endeavors of learners who are trying to gain fluency and mastery of a second language, so therefore, the rule of formal instruction in the process of learning a second language must be investigated and examined thoroughly. Moreover, it complements the best way to make instruction effective and helpful. Numerous studies have been carried out to investigate whether the ways of instruction alters the sequence of the learners' acquisition, and also, whether the learners acquire the language in the way the naturalistic learners do.
One of the most emphasized concepts about second language learning is that some individuals are more inclined to learning a second language than other individuals. But there are factors to be considered before uttering such statements, such as age, motivation, ability, and socio-psychological factors. In addition to some SLA aspirants being more successful than others, there also exists the fossilization, which denotes the phenomenon of being stuck in a stagnant state of language knowledge. Zhaohong Han in 2004 stated that a "complete acquisition of a second language is impossible." In "the course of the last 3 decades, SLA have accumulated an amazing chunk of evidence proving the empirical phenomenon of fossilization." (Han, 2004).
It is widely recognized that the "fossilization precipitated the existence of the SLA." (Gass and Selinker, 2006). The phenomenon is disputed as true because of the theory that no matter how hard the efforts the learners exert to learn, they will be in a stage where their knowledge is "stuck" quite distant from the expected target. And also, "this phenomenon also seems to affect even the most advanced learners of L2. Fossilization is a frequently discussed and yet little misunderstood notion concerning second language. The phenomenon is thought upon as the inevitable 'intermediate' difference between the learners' native language and their target language, for the implications brought about by the familiarity with the native language indirectly influences the ways in which the target language will be learned." (Gass and Selinker, 2006).
No matter the magnitude of the expertise of the instructions and means of instructions possess, there will always be a case in which fossilization seems to hamper and "hold back"