What is vocabulary? One of the most difficult questions to answer in vocabulary studies is ‘What is a word?’ and there are a variety of only partly satisfactory answers depending on the reasons for asking the question. If we want to count how long a book is, or how fast someone can speak or read in words per minute, then we need to count tokens. The sentence ‘To be or not to be, that is the question’ contains ten tokens. Even though the same word form be occurs twice, it is counted each time it occurs. When counting tokens, it is necessary to decide if we count items like I’m or we’ll as two tokens or one. If we are counting tokens in spoken language, do we count um and er as tokens, and do we count repetitions like I ... I ... I said as tokens? We can only answer these questions by examining our reasons for counting. Often we are interested in how many different words someone knows or uses.