Note: This page is still being revised.

1. Five Purposes of Definition
1. To Increase Vocabulary
2. To Eliminate Ambiguity
3. To Reduce Vagueness
4. To Explain Theoretically
5. To Influence Attitudes
2. Five Types of Definition
1. Stipulative-A definition that is given to a new term or idea. Example: Internet. Hip-hop.
2. Lexical-Reports on the meaning already assigned. Dictionary definitions tend to be too brief to really give the reader a good understanding of a complex word. Often it is necessary to look up the meaning of specialized terms in specialized resource material. Example: Compare the definition of "heart attack" in a standard dictionary and a medial textbook. In college, you generally need to use a more specialized resource when defining complex terms.
3. Percising-"a definition capable of helping to decide borderline cases that go beyond the mere lexical [or dictionary] meaning" (p. 151). Example: the term "reasonable doubt" requires an understanding of finer points than would be covered in a dictionary. These definitions tend to be longer since they need to develop the definition.
4. Theoretical-"attempts to formulate an adequate characterization of the objects to which it is applied" (p. 152). Some examples include "justice," "virtue," "the good," as well as definitions of terms such as "heat" or "temperature." (p. 152).
5. Persuasive-A definition whose purpose is to get people to accept a position: Examples: Pro-Choice (contrast with Pro-Abortion), Anti-Abortion; partial Birth Abortions (contrast with late term abortions to save the mother's life).
6. Extended-A longer definition in which many aspects of the term are analyzed. Example: What is meant by "Diversity?"
3. Various Kinds of Meaning
1. Denotation-"the collection of all those objects to which a term applies" (p. 156) Definition by listing out the objects that meet a criteria. Example: Spades, Hearts, Clubs and Diamonds are "card suits."
2. Connotation-"collection of attributes shared by all and only those objects in a term's extension" (p. 155) Example: A "skyscraper" is a building over a certain height.
1. Subjective Connotation-"the set of all attributes that a particular speaker believes to be possessed by the object" (p. 155). Example: To me, a skyscraper is a building that is more that 10 stories high.
2. Objective Connotation-"The total set of characteristics common to all objects that make up that term" (p. 155). These are not subject to individual interpretation.
3. Conventional Connotation-Generally accepted definition.
4. Techniques for Defining
1. Denotative Defintions-a definition by giving examples. Example: Mars and Venus are "planets." (Note: They are also Roman gods so the definition is not as clear as it could be.) This method can't be used for terms that don't exist such as unicorns (p. 159).
2. Connotative Definitions-a definition in which the object is described in such a way that it fits the definition. Also called definition by genus and species. The genus is the general property while the species narrows the definition to include only the defined term. Example "The word 'triangle' means a polygon having three sides". (p. 163)
3. Operational Definitions-"term applied to a given case if and only if the performance of specified operations in that case yields a specific result" (p. 162). This type of definitions is use when defining the results of how something works. Also known as a definition by process. Example: The area of a rectangle is the product of the length times the width.
5. Rules for Definition by Genus and Difference
1. The definition should state the conventional connotations of the term being defined.
2. The definition should not be circular: The definition can not be used in the formulation of a definition: Example: A circle is a circular object.
3. A definition must be neither too broad nor to narrow. Example: A "shoe" is a leather covering on the foot. (too narrow: shoes can be made out of other material.) Man is a 'featureless biped.' (too broad: Plato plucked the feathers from a chicken and then asked was it a man. (p. 167). This is one of the most common mistakes,
4. A definition must not be expressed in ambiguous, obscure or figurative language. Example: Defining "bread" as the "staff of life." Defining a wedding ring as "a matrimonial tourniquet design to stop circulation" (p. 168).
5. A definition should not be negative where it can be affirmative. It is better to define what something is rather than what it is not--if you can help it.
Some general comments:
When asked for a definition in college, it will generally fall into two types. The first is a short definition.This is generally a Lexical, Connotative or Denotative Definitions. Basically, all this shows is that you can memorize. The second kind of definition asks whether you can explain a term. Often, you will have to define the terms used in your definition to a much greater detail. This is more complex and often uses Percising, Theoretical, Operational or Extended Definitions . Often these definitions involve several paragraphs to long papers.

The term "slavery" can be looked up in a dictionary. This gives you a basic understanding of the word. However, to get a truer understanding of the term, it necessary to consult longer works that go into all the various aspects of slavery. The term "immigrant" can be looked up in a dictionary and define in a single sentence; however, the concept of what an immigrant is can take several pages to go into. This can be done by giving a detailed example or explaining the various aspects of what it means to be an immigrant.

From Copi, Irving. Introduction to Logic. 6th Ed. Macmillian:New York, 1982.