Words as types and words as tokens

How many words are there in the following sentence?

(1) Mary goes to Edinburgh next week, and she intends going to Washington next month.

If we take as a guide the English spelling convention of placing a space between each word, the answer seems clearly to be fourteen. But there is also a sense in which there are fewer than fourteen words in the sentence, because two of them (the words to and next) are repeated. In this sense, the third word is the same as the eleventh, and the fifth word is the same as the thirteenth, so there are only twelve words in the sentence. Let us say that the third and the eleventh word of the sentence at (1) are distinct tokens of a single type, and likewise the fifth and thirteenth word. (In much the same way, one can say that two performances of the same tune, or two copies of the same book, are distinct tokens of one type.)

The type–token distinction is relevant to the notion ‘word’ in this way. Sentences (spoken or written) may be said to be composed of word-tokens, but it is clearly not word-tokens that are listed in dictionaries. It would be absurd to suggest that each occurrence of the word next in (1) merits a separate dictionary entry. Words as listed in dictionaries entries are, at one level, types, not tokens – even though, at another level, one may talk of distinct tokens of the same dictionary entry, inasmuch as the entry for month in one copy of the Concise Oxford Dictionary is a different token from the entry for month in another copy.

Is it enough, then, to say that characterization 2. (words as building-blocks) relates to word-tokens and characterization 1. (words as meaningful units) relates to word-types? The term word would be ambiguous between a ‘type’ interpretation and a ‘token’ interpretation; but the ambiguity would be just the same as is exhibited by many other terms not specifically related to language, such as tune: a tune I heard this morning may be ‘the same’ as one I heard yesterday (i.e. they may be instances of the same type), but the two tokens that I have heard of it are distinct. However, the relationship between words as building-blocks and as meaningful units is not so simple as that, as we shall see. So, while it is important to be alert to type–token ambiguity when talking about words, recognizing this sort of ambiguity is by no means all there is to sorting out how characteristics 1. and 2. diverge.