Wilkins (1972), an early advocate of the communicative approach, clearly indicated that learning vocabulary is as important as learning grammar. Whether or not the leaner has reached a level close to the native speaker can be judged by his or her ability to use and pronounce collocations well. It is argued that lexical competence is at the heart of communicative competence and according to Verhallen&Schoonen (1998), this lexical competence can be a “prediction of academic success” (P. 452). Allen (1983) also underlines this point of view by stating that “ lexical problems often interfere with communication; communication breaks down when people don't use the right words” (P. 05). In another statement Wilkins (1974) states: “Without grammar very little can be conveyed, without vocabulary nothing can be conveyed”. The role of vocabulary is so important that Lewis (1993) states that "vocabulary is the core of language". Richards (1976: 77) explains the role of vocabulary in light of eight assumptions regarding the nature of lexical competence, and suggests these assumptions should be kept in mind in the teaching of vocabulary. Some of his hypotheses related to this study are summarized as