Understanding the difference between denotation and connotation is important to understanding definitions and how concepts are used. Unfortunately, that is complicated by the fact that these terms can be used in two different ways: grammatical and logical. Even worse, both uses are worth keeping in mind and both uses are relevant to project of logical, critical thinking.
In grammar, a word’s denotation is whatever the word directly refers to, roughly equivalent to its lexical definition. Thus, the word “atheist” denotes a person who disbelieves in or denies the existence of gods. A word’s connotation refers to any subtle nuances that might or might not be intended by its use. For example, one possible connotation for the word “atheist” might be someone who is immoral and wicked, depending upon who is doing the speaking or listening.
Separating grammatical denotation from connotation is important because while one might assume that a word’s denotation is fully intended, whether a word’s connotations are intended is much more difficult to determine. Connotations are often emotional in nature, and thus if they are intended, it may be for the purpose of swaying a person’s emotional reactions rather than the logical evaluation of an argument.
If there are misunderstandings about how a person is using a word in a particular debate, a primary source of that misunderstanding might lie in the word’s connotations: people might be seeing something not intended or the speaker may be intending something people don’t see. In constructing your own arguments, it’s a good idea not merely to look at what your words denote, but also what they connote.
In logic, the uses of denotation and connotation are very different. The denotation, or extension, of a term is the list of a class of objects referred to by the word (think of it as “how far does this word extend?”). Thus the word “planet” denotes specific objects such as Venus, Earth, Jupiter, and Neptune. Whether it also denotes an object like “Pluto” is a matter of some debate among astronomers for reasons I will explain shortly.
The connotation, or intension, of a word is the list of attributes shared by all members of the class named by the word (think of it as “by using this word, what do I intend?”). Thus the word “planet” connotes certain characteristics which astronomers have decided differentiate certain objects from other objects like comets, stars, and asteroids. The debate over whether the word “planet” denotes “Pluto” is due to the fact that astronomers disagree on what sorts of attributes are connoted by the word “planet,” and hence whether “Pluto” has the right attributes to qualify as a planet.
