Definition

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For alternative meanings see definition (disambiguation)

A definition is the association of a word or phrase and its meaning.

Table of contents

1 Philosophy 2 Some background: extension, intension, ambiguity, and vagueness 3 The meaning of 'definition' (a definition)

Philosophy

Philosophers discuss the meaning, function, and possibility of offering definitions. It is typical (e.g., in college logic texts) to distinguish a number of different kinds and techniques of definition, including:

1. dictionary or lexical definition
2. intensional definition
3. extensional definition
4. ostensive definition
5. stipulative definition
6. operational definition
7. theoretical definition
8. persuasive definition
9. definition by genus and difference
10. circular definition

Philosophers are constantly asking for definitions, or accountss, or analyses, of various philosophical concepts such as existence, causality, meaning, knowledge, goodness, justice, beauty, art, and so on. Thus they hope to clarify in some manner the most pervasive concepts descriptive of the universe and human life.

Some background: extension, intension, ambiguity, and vagueness

Just as arguments can be good or bad, definitions can be good or bad. A definition is supposed to give us the meaning of a word; there are certain aspects of the topic of definition that cannot be understood until one reviews a few features of meaning. We will therefore review the topics of extension, intension, ambiguity, and vagueness.

Begin with the distinction between the extension and the intension (both spelled with an "s") of a word. This is very similar to a familiar distinction--between a word's denotation and connotation. Take the word 'bachelor'. The extension of this word is all and only the bachelors in the world. The extension of this word would include several hundreds of millions of men. The intension of this word can be stated relatively briefly, because it includes just two properties: the property of being a man, and the property of being unmarried. So all bachelors are unmarried men, and only bachelors are unmarried men.

The sort of definition that philosophers are interested in, insofar as they are interested in definitions at all, is one that identifies the intension, not the extension of the word. An excellent definition of the word 'bachelor' is 'unmarried man'. A less-than-excellent definition of the same word would be a list of names of all of the men in the world who are bachelors. Aside from being practically impossible, such a list is just not what we are looking for. After all, what we are interested in is a description of what all those things we call 'bachelors' have in common, which distinguishes them from all non-bachelors. A list of all bachelors would give us no means to determine whether any new human is a bachelor or not.

Notice now that there are two different ways in which the meanings of words can be unclear. Words can be unclear in the sense of being ambiguous, or in the sense of being vague (or, it so happens, in both senses). Most words are, in fact, both ambiguous and vague. This is not a skeptical or even a controversial claim; to say that many, or perhaps even most, words are both ambiguous and vague is not to say that they have no meaning. It is to say, first, that many individual words many distinct senses; and, second, that those senses are often, in ordinary language, not so precise as to be able to allow us to rule that the word does or does not apply in every case. So certainly, a word that is both ambiguous and vague can have a rich fund of meaning.

The meaning of 'definition' (a definition)

With this background, it will be easier to discuss definitions. Suppose we have decided on some word, or concept associated with the word, to define. Suppose also that we have identified which sense of the word we are interested in, and we have noted clear cases, some unclear cases, and some borderline cases of the application of the word. So we ask: how can this word be defined? We already know that we want a description of the intension of the word: that is, we want an account of the set of properties that characterizes all and only members of the extension. In that case, it seems the following is a servicable account of the meaning of '(intensional) definition':

The definition of a concept, or of (a given sense of) a word or phrase, is a description of its intension--that is, the set of properties that characterizes all and only members of the extension of the word; the extension is all the things that the concept, word, or phrase applies to.

Some philosophers have some criticisms of this sort of definition of the word 'definition'; or perhaps it would be better to say that some philosophers think that it is, for various reasons, impossible to give definitions of most concepts, words, and phrases. Two prominent examples are Wittgenstein and Quine. Even if those philosophers are right, they will, most of them, still acknowledge that in philosophy we should do something like give definitions of important philosophical concepts.

See also fallacies of definition, Ramsey-Lewis method, analytic proposition, synthetic proposition.