A sememe (from Greek σημαίνω (sēmaínō), meaning "mean, signify") is a semantic language unit of meaning, correlative to a morpheme. The concept is relevant in structural semiotics.

A sememe is a proposed unit of transmitted or intended meaning; it is atomic or indivisible. A sememe can be the meaning expressed by a morpheme, such as the English pluralizing morpheme -s, which carries the sememic feature [+ plural]. Alternatively, a single sememe (for example [go] or [move]) can be conceived as the abstract representation of such verbs as skate, roll, jump, slide, turn, or boogie. It can be thought of as the semantic counterpart to any of the following: a meme in a culture, a gene in a genetic make-up, or an atom (or, more specifically, an elementary particle) in a substance. A seme is the name for the smallest unit of meaning recognized in semantics, referring to a single characteristic of a sememe.

There are five types of sememes: two denotational and three connotational, with connotational occurring only in phrase units (they do not reflect the denotation):