O - Definition and Overview

O is the fifteenth letter of the Latin alphabet.

In Greek (Omikron), Etruscan and Latin O stood for the vowel /o/. Although Semitic 'Ajin was used in some alphabets to transcribe [o], the sound value was usually consonantic: [?/] (as the Arabic letter ع called 'Ajn').

Oscar represents the letter O in the NATO phonetic alphabet. In the International phonetic alphabet, [o] represents the close-mid back rounded vowel.

In medicine, O is one of the human blood types.

Ō is also a Japanese family name. Ō (often romanized as "Oh" or "O") is a rare family name which is equivalent to Wang in Chinese. Ō is the way Japanese pronounce the character 王. Most of the Japanese with such a surname are Chinese descendants.

People who have this name include:

• O Rissei, a famous Go player
• Sadaharu Oh, the all-time home run king