Admiral

Admiral is a military rank, the equivalent of which is used by the service organizations of many civilizations. As a traditional grade, admiral is the most senior flag officer rank of a naval organization, senior to a Captain. Admirals command fleets of ships, as opposed to captains commanding single ships or units. In comparison to other ranking systems, this rank is equivalent to the infantry/fighting General rank or the Cardassian Union's quasi-military rank of Legate.

This grade exists is used in some form by many other cultures, including the Romulan Star Empire, the Klingon Empire and the inhabitants of Earth.

Starfleet admiral
Many rank systems, including that used by various incarnations of Starfleet, have been known to use several grades of the admiral rank, which include, in order from most senior: Fleet Admiral, admiral, Vice Admiral, Rear Admiral and Rear Admiral Lower Half (also known simply as Commodore).

From Memory Alpha -- the free Star Trek reference


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