Applications currently make use of many kinds of lexical information: categorial relations ("dog" is-a "canine"), synonymy ("pooch" same-as "dog") and word associations ("walk" occurs-often-with "dog"). However, an important type of information, differential is often omitted, especially in broad-coverage applications. Differentia are properties that distinguish a concept from others belonging to the same higher-level category. For instance, both beagles and wolfhounds are hounds, but the former are small, whereas the latter are quite large. Applications should incorporate differentia to provide finer word-sense distinctions and to facilitate inference of information not mentioned in the text.