The chapter reviews some of the ways that linguistics has been used in second language acquisition (SLA) and bilingual research, ranging from overall linguistic theories to research techniques, and evaluates the relationship between linguistics and SLA research. In an ideal world, the discipline of linguistics would set out the nature of language in general and would describe individual languages in particular. The meanings of words, covered in semantics, in linguistics are barely touched on in SLA research; neurolinguistics, too, is mentioned only in the context of age. While Chomsky’s quotations relate primarily to the UG model, these do show the basic monolingual assumption in linguistics. The linguistic intuition method of the linguists is then closer to a single sentence competence mode, the SLA researchers’ grammaticality judgments test to an experiment-based approach: linguists rarely give the statistical significance of their intuitions. Bilingualism researchers are more reluctant to subordinate their bilingual subjects to monolinguals than SLA researchers.