In the study of word meanings, opposites are words that cannot be true at the same time and are part of a pair. For example, if something is even, it cannot be odd. This is called a "binary" relationship because there are two parts in the pair. The connection between opposites is called opposition. To find an opposite, people often ask, "What is the opposite of X?"

The word "antonym" (and the related term "antonymy") is often used to describe opposites, but it has more specific meanings. Graded antonyms are pairs of words with opposite meanings that exist on a range of possibilities, such as "hot" and "cold." Complementary antonyms are pairs of words with opposite meanings that do not exist on a range, such as "push" and "pull." Relational antonyms are pairs where the opposite only makes sense when considering the relationship between the two words, such as "teacher" and "pupil." Some scholars, like Lyons (1968, 1977), define "antonym" to mean graded antonyms, while others, like Crystal (2003), caution that the terms "antonymy" and "antonym" should be used carefully depending on the context.

General discussion

Opposition is a type of meaning connection where one word has a meaning that is the opposite or very different from another related word. Some words do not have a direct opposite because the language does not include a word for it. For example, the word "devout" does not have a direct opposite, but we can imagine a scale of devoutness, where "devout" is at the positive end and the negative end is missing a word. In some cases, opposites can be created by adding prefixes like "un-" or "non-," though some combinations are more common than others. For instance, "undevout" is found in an old dictionary, and "non-person" could theoretically become "non-platypus."

Some words appear to be formed with a prefix that suggests opposition, but the root word does not exist. An example is "inept," which seems to be "in-" + "ept," but "ept" is not a real word. These words are called unpaired words. Opposites can be seen as a special type of incompatibility. Incompatible words cannot be used together in a way that makes sense. For example, if something is "fast," it cannot be "slow" at the same time.

Examples of incompatible word pairs include "cat" and "dog," as well as "fast" and "slow," and "stationary" and "moving." This incompatibility can be seen in statements like:
"It's fast" means "It's not slow."

Cruse (2004) describes some basic features of opposites. Some planned languages use prefixes to create opposites and reduce the number of words needed. For example, Esperanto uses "mal-" (as in "bona" = "good" and "malbona" = "bad"), Damin uses "kuri-" (as in "tjitjuu" = "small" and "kuritjitjuu" = "large"), and Newspeak uses "un-" (as in "ungood" = "bad").

Some classes of opposites include:

Types of antonyms

An antonym is a word that has the opposite meaning of another word. Each word in the pair is the opposite of the other. A word can have more than one antonym. There are three types of antonyms based on how their opposite meanings are related.

A gradable antonym is a pair of words with opposite meanings that exist on a scale or range. For example, "hot" and "cold" are opposites on a temperature scale, making them gradable antonyms. Other examples include: heavy : light, fat : skinny, dark : light, young : old, early : late, empty : full, dull : interesting.

A complementary antonym, sometimes called a binary or contradictory antonym (Aarts, Chalker & Weiner 2014), is a pair of words with opposite meanings that are not on a scale. For example, "odd" and "even" are opposites but not on a scale, so they are complementary antonyms. Other examples include: mortal : immortal, exit : entrance, exhale : inhale, occupied : vacant.

A relational antonym is a pair of words that describe opposite roles or positions within a relationship. For example, "teacher" and "pupil" are opposites in the context of their relationship, even though they are not direct opposites. This makes them relational antonyms. Other examples include: husband : wife, doctor : patient, predator : prey, teach : learn, servant : master, come : go, parent : child.

Auto-antonyms

An auto-antonym is a word that can mean the opposite of itself, depending on how it is used in a sentence or what it is being compared to.