Speakers take for granted every day both that there are words for things and that words differ in meaning. We have assumed that the stock of words speakers draw on can be thought of as forming a mental dictionary. But it is more than that. Dictionaries list only words that are well established, but speakers can also construct new words, made just for the occasion. So the lexical resources speakers make use of must include both well-established terms, known to the speech community, and novel ones, coined for special occasions. In this chapter, I take up conventionality, that well-established words have conventional meanings, and contrast, that words differ in meaning. These two together guide speakers in their use of the lexicon. The emphasis here is on their general consequences. In the next chapter, I explore their consequences for acquisition.

Conventionality

The principle of conventionality is the following: “For certain meanings, there is a form that speakers expect to be used in the language community.” That is, if a conventional term expresses what they mean, speakers should use it. If they don't do so, or if they use a term in a non-conventional way, they are liable to be misunderstood.