The book addresses the role of the L1 (first language)-based concept categorization in L2 (second language) vocabulary learning from a cognitive linguistic perspective. The author hypothesizes that the patterns of one’s L1-based concept categorization will be present in his or her L2 vocabulary learning as well. The two characteristics pertaining to concept categorization under investigation are the prototypicality and the basic-level effects. The results show that the psychological salience of the basic-level and the prototypical concepts in one’s L1-based conceptual system is related to better retention and faster retrieval of the corresponding L2 words. The author argues that these two effects are dynamic in L2 contexts, being influenced by factors such as concept familiarity, formal instruction and exposure to the specific culture.