Dictionary

Part of speech: noun (n.)

1. O, the fifteenth letter of the English alphabet, derives its form, value, and name from the Greek O, through the Latin. The letter came into the Greek from the Phoenician, which possibly derived it ultimately from the Egyptian. Etymologically, the letter o is most closely related to a, e, and u; as in E. bone, AS. ban; E. stone, AS. stan; E. broke, AS. brecan to break; E. bore, AS. beran to bear; E. dove, AS. dufe; E. toft, tuft; tone, tune; number, F. nombre. The letter o has several vowel sounds, the principal of which are its long sound, as in bone, its short sound, as in nod, and the sounds heard in the words orb, son, do (feod), and wolf (book). In connection with the other vowels it forms several digraphs and diphthongs. See Guide to Pronunciation, §§ 107-129.

2. Among the ancients, O was a mark of triple time, from the notion that the ternary, or number 3, is the most perfect of numbers, and properly expressed by a circle, the most perfect figure. O was also anciently used to represent 11: with a dash over it (O O, n.; pl. O's or Oes (.

3. The letter O, or its sound. "Mouthing out his hollow oes and aes." Tennyson.

4. Something shaped like the letter O; a circle or oval. "This wooden O [Globe Theater]". Shak.

5. A cipher; zero. [R.] Thou art an O without a figure. Shak.

Part of speech: adjective (a.)

One. [Obs.] Chaucer. "Alle thre but o God." Piers Plowman.

Part of speech: interjection (interj.)

An exclamation used in calling or directly addressing a person or personified object; also, as an emotional or impassioned exclamation expressing pain, grief, surprise, desire, fear, etc. For ever, O Lord, thy word is settled in heaven. Ps. cxix. 89. O how love I thy law ! it is my meditation all the day. Ps. cxix. 97.

Part of speech: noun (n.)

A prefix to Irish family names, which signifies grandson or descendant of, and is a character of dignity; as, O'Neil, O'Carrol.

Part of speech: preposition (prep.)

A shortened form of of or on. "At the turning o' the tide." Shak.