Progress toward establishing a model of lexical development to guide vocabulary acquisitionresearch requires more precise specification of the various dimensions of lexical competence, theinterrelationships among them, and how they interface with processes of word learning and use.Three dimensions of lexical competence are proposed: (a) partial to precise knowledge, (b) depthof knowledge, and (c) receptive to productive use ability. The relationship between the twoknowledge dimensions and the acquisition of word meaning is considered, with emphasis on thecomplexity of the semantization1 process and on the need for redefining lexicaldevelopment as both item-learning and system-changing. The adequacy of the three-dimensionaldescription as a reflection of the process of vocabulary development is then discussed.Consideration of the nature of the developmental interrelationships among the dimensions raisestwo further questions: (a) Is depth of knowledge a prerequisite for developing precisecomprehension? and (b) Are precise knowledge and depth of knowledge prerequisites for a wordto become productive?