A definition identifies the essential qualities and limits the meaning of a term. A definition answers the question "What is it?" A definition defines a term (bottle) - not a thing (baby bottle).
Use definition when:
1. You use a term your audience may not know (e.g., prototype).
2. When a term has several possible meanings (e.g., courage).
3. When a term may be too vague without further explanation (e.g., liberal).
4. When you want your audience to know that you're using a term which holds a particular technical or professional meaning (e.g., Victorian Literature).
Different defining methods:
Definition by word substitution offers a word or phrase that could be used in place of the unknown term. DO NOT use the term in its definition; this results in a circular definition.
Yes: Democracy is "a government in which the supreme power is vested in the people."
No: Democracy is a democratic form of government.
Definition by synonym equates the term to be defined with a term that has about the same meaning. DO NOT use a synonym that your audience will not be familiar with.
Yes: A lanai, or porch, ran the length of the house. (Nearly everyone knows what a porch is.)
No: A prototype is an archetype. (Few people know what an archetype is.)
Definition by negation-telling what something is not-is not helpful unless it is combined with a positive definition.
Yes: To praise is not to applaud, celebrate, commend, flatter, or puff-but rather it is to nurture the human spirit.
No: A horse is not an alligator.
You can define by citing an example: Democracy is the type of government that can be found in theU.S.A., Great Britain, and Canada.
Rhetorical definitions are personal and subjective, and they require development. They ask for explanation.
Example: "Time is but the stream I go fishing in." (Henry Thoreau)
Definition by function explains what something does or how something works.
Definition by structure tells how something is organized or put together.
By Function: A plumb bob offers a perfect reference for vertical alignment when suspended from above because its weight hangs straight down.
By Structure: A plumb bob is a pointed weight at the end of a string.
An analytical definition places the term in a class and then explains how that term differs from other terms in the same class.
A gibbon, for example, is in the same class of apes as an orangutan, but it differs in size and geographic location.
Definiendum: the term being defined. Definiens: the terms used for defining.
Definiens have two parts: (1) genus, the general class or first level of classification and (2) differentia, the special characteristics of the genus.
EXAMPLE: A vegetarian is a person who eats no meat.
Definiendum: vegetarian. definiens: person who eats no meat.
genus: person differentia: eats no meat.