A synonym is a word or phrase that means exactly or nearly the same as another word or phrase in the same language. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greek syn () (“with”) and onoma () (“name”). An example of synonyms are the words begin, start, and commence. Words can be synonymous when meant in certain senses, even if they are not synonymous in all of their senses. For example, if we talk about a long time or an extended time, long and extended are synonymous within that context. Synonyms with exact interchangeability share a seme or denotational sememe, whereas those with inexactly similar meanings share a broader denotational or connotational sememe and thus overlap within a semantic field. Some academics call the former type cognitive synonyms to distinguish them from the latter type, which they call near-synonyms. In the figurative sense, two words are sometimes said to be synonymous if they have the same connotation: Metonymy can sometimes be a form of synonymy, as when, for example, the White House is used as a synonym of the administration in referring to the U.S. executive branch under a specific president. Thus a metonym is a type of synonym, and the word metonym is a hyponym of the word synonym. The analysis of synonymy, polysemy, and hyponymy and hypernymy is vital to taxonomy and ontology in the information-science senses of those terms. It has applications in pedagogy and machine learning, because they rely on word-sense disambiguation and schemas.