Definition

A definition is a statement that explains the meaning of a term (a word, phrase, or other set of symbols). The term to be defined is the definiendum. A term may have many different senses or meanings. For each such specific sense, a definiens is a cluster of words that defines that term with reference to the speaker's immediate intended meaning.

For example, in formal languages like mathematics, a "stipulative" definition guides a specific discussion. A stipulative definition can only be disproved by showing a logical contradiction. But a "descriptive" definition can be shown to be "right" or "wrong" with reference to general usage.

A chief difficulty in the management of definitions is the necessity of using other terms that are already understood or whose definitions are easily obtainable. The use of the term in a simple example may suffice. A dictionary definition typically contains additional details, such an etymology, obsolete meanings, and the language or languages of its origin.

A precising definition extends the descriptive dictionary definition (lexical definition) of a term for a specific purpose by including additional criteria, which narrow the set of things that meet the definition.

C.L. Stevenson has identified persuasive definition as a form of stipulative definition which purports to state the "true" or "commonly accepted" meaning of a term, while in reality stipulating an altered use (perhaps as an argument for some specific belief). Stevenson has also noted that some definitions are "legal" or "coercive" — their object is to create or alter rights, duties, or crimes.