Apposition is a grammatical construction in which two elements, normally noun phrases, are placed side by side, with one element serving to define or modify the other. When this device is used, the two elements are said to be in apposition. For example, in the phrase "my friend Alice", the name "Alice" is in apposition to "my friend".

Traditionally, appositions were called by their Latin name appositio, although the English form is now more commonly used. It is derived from Latin: ad ("near") and positio ("placement").

Apposition is a figure of speech of the scheme type, and often results when the verbs (particularly verbs of being) in supporting clauses are eliminated to produce shorter descriptive phrases. This makes them often function as hyperbatons, or figures of disorder, because they can disrupt the flow of a sentence. For example, in the phrase: "My wife, a nurse by training, ...", it is necessary to pause before the parenthetical modification "a nurse by training".

Apposition can either be restrictive, or non-restrictive where the second element parenthetically modifies the first.