The motivational base of this study lies in the real-life problem faced by many L2 learners: How can learners achieve target-like lexical competence? It does not take much to demonstrate that knowing a dictionary definition alone is not enough, but how learning from context actually leads to accuracy of production has remained unclear. The present article addresses this issue by proposing a cognitive model that illustrates the role of context and definition as well as L1 translation in the acquisition of conceptual knowledge. Drawing on studies of L1 acquisition, particularly the usage-based theory of language acquisition, this paper discusses in depth how L2 acquisition differs from L1 acquisition in various aspects.Meanwhile, it accounts for the development of accuracy by adopting a gap-filling-oriented acquisition view. In summary, by providing a systematic account for how various components contribute to the acquisition of a word, the proposed model offers a solution to several important debates in SLVA besides giving new insights into a range of pedagogical and learning issues.