In cognitive linguistics, metonymy refers to the use of a single characteristic to identify a more complex entity and is one of the basic characteristics of cognition. It is common for people to take one well-understood or easy-to-perceive aspect of something and use that aspect to stand either for the thing as a whole or for some other aspect or part of it.
Cognitively, metonymy is attested in cognitive processes underlying language (e.g. the infant's association of the nipple with milk). Objects that appear strongly in a single context emerge as cognitive labels for the whole concept, thus fueling linguistic labels such as "sweat" to refer to hard work that might produce it.
The word metonymy is derived from Greek μετά- beyond/changed and -ωνυμία, a suffix used to name figures of speech from ὄνυμα name (OED)) (IPA: .