Book excerpt: Measuring Second Language Vocabulary Acquisition provides an examination of the background to testing vocabulary knowledge in a second language and in particular considers the effect that word frequency and lexical coverage have on learning and communication in a foreign language. It examines the tools we have for assessing the various facets of vocabulary knowledge such as aural and written word recognition, the link with word meaning, and vocabulary depth. These are illustrated and the scores they produce are demonstrated to provide normative data. Vocabulary acquisition from course books and in the classroom in examined, as is vocabulary uptake from informal tasks. This book ties scores on tests of vocabulary breadth to performance on standard foreign language examinations and on hierarchies of communicative performance such as the CEFR.