Polysemy is a key question in the field of semantics. Empirical observations, analysis and description of polysemy are important for theoretical considerations and development as well as for applied linguistics, e.g. lexicography.

Polysemy occurs when a lexical unit or a construction is used to represent different but also related meanings. Polysemous variation is either conventional and systematic or the result of merely incidental, contextually induced meaning shifts. A polyseme has one or more distinct and entrenched sense potentials, but they sometimes combine or fuse in actual language use. In addition, there are more general types of regular polysemy that are only pragmatically instantiated, as well as idiosyncratic and unpredictable meaning changes. By comparison, a monosemic element has only one conventional sense, while homonyms just happen to be formally identical although their meanings are not related.

Important factors in polysemous variation are (i) the occurrence of different types of meaning, or language functions, (ii) differences in experiential domain connections, and (iii) differences in sense relations. The following types of polysemous variation have been recognised: collocational tailoring, domain shift, metaphor, metonymy, perspective shift, value reversal, irony, emotive colouring, interpersonal signal, and idiom breaking.