Research has conclusively shown that learners need a large vocabulary to function proficiently in their second language (especially in English). In addition to this large vocabulary size, learners must also know a great deal about each individual lexical item in order to use it well. This often referred to as the quality or depth of vocabulary knowledge, and is as important as vocabulary size. Most laymen (including many teachers and learners) might consider a lexical item ‘learned’ if the spoken/written form and meaning are known. While it is true that the form-meaning link is the first and most essential lexical aspect which must be acquired, and may be adequate to allow recognition, much more must be known about lexical items, particularly if they are to be used productively.

While the ideal case would be where learners have a large lexicon in which each item is well known, it is possible to think of cases where learners have a small lexicon of well-practiced and well-known items. Conversely, learners using extensive rote memorization might be found to have large vocabularies in which all that is known about the individual items is the memorized meanings.

While these extremes do exist, what does the research show is the typical relationship between size and depth? Some researchers have even suggested there is little real difference between the two constructs in practice (e.g. Vermeer, 2001). This presentation will report on an extensive critical review of vocabulary studies in which both size and depth have been measured. The interpretation of results will involve issues including automaticity and word associations, the difficulty of measuring depth, and the incremental nature of vocabulary acquisition. Based on the meta-analysis, the presenter will present a framework for conceptualizing the various facets of vocabulary knowledge.