Admiral is the rank, or part of the name of the ranks, of the highest naval officers. It is usually abbreviated to "Adm" or "ADM".
The rank is generally thought to have originated in Sicily from a conflation of (アラビア語:أمير البحر), ''amīr al-baḥr'', "commander of the sea", with Latin ''admirabilis''〔(【引用サイトリンク】title=Online Etymology Dictionary )〕 ("admirable") or ''admiratus'' ("admired"), although alternative etymologies derive the word directly from Latin, or from the Turkish military and naval rank miralay.
In the Commonwealth and the U.S., a "full" admiral is equivalent to a "full" general in the army, and is above vice admiral and below admiral of the fleet (or fleet admiral). In NATO, admirals have a rank code of OF-9.
The word "admiral" in Middle English comes from Anglo-French ''amiral'', "commander", from Medieval Latin ''admiralis'', ''admirallus''. These themselves come from Arabic "amīr", or ''amīr al-'' (), "commander of", as in ''amīr al-baḥr'' (), "commander of the sea".〔(Merriam-Webster on-line dictionary )〕 Crusaders learned the term during their encounters with the Muslim Arabs, perhaps as early as the 11th century.
The Norman Roger II of Sicily (1095–1154), employed a Greek Christian known as George of Antioch, who previously had served as a naval commander for several North African Moslem rulers. Roger styled George in Abbasid fashion as "Amir of Amirs", i.e. "Commander of Commanders", with the title becoming Latinized in the 13th century as "''ammiratus ammiratorum''".〔Abulafia (2011).〕
The Sicilians and later Genoese took the first two parts of the term and used them as one word, ''amiral'', from their Aragon opponents. The French and Spanish gave their sea commanders similar titles while in Portuguese the word changed to ''almirante''. As the word was used by people speaking Latin or Latin-based languages it gained the "d" and endured a series of different endings and spellings leading to the English spelling "admyrall" in the 14th century and to "admiral" by the 16th century.
The word "admiral" has today come to be almost exclusively associated with the highest naval rank in most of the world's navies, equivalent to the army rank of (full) general. However, this wasn't always the case; for example, in some European countries prior to the end of World War II, admiral was the third highest naval rank after general admiral and grand admiral.
The rank of admiral has also been subdivided into various grades, several of which are historically extinct while others remain in use in most present day navies. The Royal Navy used colours (red, white, and blue, in descending order) to indicate seniority of its admirals until 1864; for example, Horatio Nelson's highest rank was vice admiral of the white. The generic term for these naval equivalents of army generals is flag officer. Some navies have also used army-type titles for them, such as the Cromwellian "general at sea".
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』