Number of different words (NDW) in a language sample is a commonly-used, evidence-based technique for assessing lexical diversity. As a quantitative measure, NDW is limited in its ability to capture other aspects of lexical ability, such as the use of rare or advanced words. This project aimed to identify multiple measures of lexical ability and to determine whether these measures were correlated. Audio language samples of preschool children were transcribed and analyzed for language productivity, lexical density, lexical diversity and lexical sophistication. Results were interpreted within a clinical framework for effective assessment of vocabulary.