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What are the genus and differentiae in a dictionary definition?
The traditional rules of definition are based on Aristotle's analysis. The word, called the definiendum in Latin, to be defined is identified by genus and differentia. That is, the word must first be defined according to the class (genus) of things to which it belongs. Then the word must be distinguished (differentia(ted) from the other things within that class. When "bread" is defined as 'a usually baked and leavened food', 'food' is the genus (i.e., bread is a food) and 'usually baked and leavened' (as well as the rest of the definition) constitutes the differentia. Simplified, if you defined "bachelor" as an 'unmarried man', 'man' is the genus and 'unmarried' is the differentia. However, many dictionary entries cannot be defined in this classical way. This formula works well for many nouns, but it does not work for most verbs, adverbs, adjectives, and other parts of speech. The genus is a superordinate word (hyperonym) to which the word to be defined is subordinate (hyponym). For example, the word "fir" can be defined as a 'tree' (genus) 'with evergreen needles' (differentia). The rules that lexicographers try to follow in defining include: 1) supplying the genus and differentia, 2) making sure the definition must be neither too broad nor too narrow, 3) making the definition state essential attributes (rather than trivial ones), 4) keeping the definition from being circular (requiring the user to look up another word), 5) making the definition positive and not negative unless absolutely necessary, and 6) avoiding vagueness, obscurity, and metaphor in the explanation.