While the words canary, cormorant, dove, duck, flamingo, parrot, pelican and robin are all equally co-hyponyms of the superordinate bird, they are not all considered to be equally good examples of the category “bird.” According to some researchers, the most characteristic instance of the category “bird” is robin. The idea of “the characteristic instance” of a category is known as the prototype. The concept of a prototype helps explain the meaning of certain words, like bird, not in terms of component features (e.g. “has feathers,” “has wings”), but in terms of resemblance to the clearest example. Thus, even native speakers of English might wonder if ostrich or penguin should be hyponyms of bird (technically they are), but have no trouble deciding about sparrow or pigeon. These last two are much closer to the prototype.

Given the category label furniture, we are quick to recognize chair as a better example than bench or stool. Given clothing, people recognize shirts quicker than shoes, and given vegetable, they accept carrot before potato or tomato. It is clear that there is some general pattern to the categorization process involved in prototypes and that it determines our interpretation of word meaning. However, this is one area where individual experience can lead to substantial variation in interpretation and people may disagree over the categorization of a word like avocado or tomato as fruit or vegetable. These words seem to be treated as co-hyponyms of both fruit and vegetable in different contexts.