Abstract
Investigations into the vocabulary size of mother-tongue speakers of English have led to a range of different findings. A survey of results reveals estimations which vary from 3 000 to 216 000 words. This paper examines possible reasons for the discrepancy in results, primarily, the assumptions made by researchers as to what constitutes a word and the issue of what it means to know a word. Some consideration is also given to the procedures followed in compiling a vocabulary test.