DEFINITION, the sheaving the mean ing of one word by several other riot sy nonymous terms. The meaning of words being only the ideas they are made to stand for by him that uses them, the meaning of any term is then sheaved, or the word is defined, when by other words the idea it is made the sign of, and is an nexed to it in the mind of the speaker, is, as it were, represented and set before the view of another ; and thus its signifi cation is ascertained. This is the only end and use of definitions, and therefore the only measure of what is, or is not, a good definition.
The names then of simple ideas are ihcapable of being defined, because the several terms of a definition signifying se veral ideas, they can altogether by no means represent an idea which has no composition at all ; and therefore a defi nition, which is properly but chewing the meaning of any one word by several others, not signifying the same each, can in the names of simple ideas have no place. Definitions which then take place in com pound ideas only are of two sorts the definition of the name, which is the ex planation of what any word means ; and the definition of the thing, which explains in what the nature of that thing consists.
The special rules for a good definition are these : I. A definition must be uni versal, or adequate, that is, it must agree to all the particular species, or individu als, that are included under the same idea. 2. It must be proper, and peculiar to the thing defined, and agree to that alone. These two rules being observed, will always render a definition reciprocal with the thing defined, that is, the defi nition may be used in the place of the thing defined ; or they may be mutually affirmed concerning each other. 3. A definition should be clear arid plain ; and indeed it is a general rule concerning the definition both of names and things, that no word should be used in either of them, which has any difficulty in it, unless it has been before defined. 4. A defini tion should be short, so that it must have no tautology in it, nor any words super fluous. 5. Neither the thing defined, nor a mere synonymous name, should make any part of the definition.