1911 Encyclopædia Britannica/Metonymy

METONYMY (Gr. μετωνυμία, change of name, from μετά, denoting change, and ὄνομα, name), a figure of speech, in which the name of one thing is changed for that of another, to which it is related by association of ideas, as having close relationship to one another. Thus “sceptre,” “throne,” “crown,” are used for royal power or authority, “hearth and home” is used for “country,” &c.

“Synecdoche” (Gr. συνεκδοχή, from συνεκδέχεσθαι, to join in receiving) is a rhetorical figure similar to metonymy, in which the part is used for the whole or vice versa, thus “hands” is used for the members of the crew of a vessel; a regiment of infantry is said to number so many “bayonets,” &c.