from The American Heritage® Dictionary of the English Language, 5th Edition.

  • interjection Used before the name of or a pronoun referring to a person or thing being formally addressed.
  • interjection Used to express surprise or strong emotion.
  • abbreviation offense
  • abbreviation offensive
  • abbreviation office telephone number
  • abbreviation Baseball out
  • abbreviation outside
  • abbreviation outstanding
  • abbreviation Sports overtime

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The fifteenth letter of the basic modern Latin alphabet.
  • noun chemistry Symbol for oxygen.
  • noun mathematics The upper bound function also known as big O.
  • noun The fifteenth letter of the English alphabet, called o and written in the Latin script.
  • abbreviation cricket The number of overs bowled
  • noun A blood type that lacks A or B antigens and may only receive transfusions of similar type O blood, but may donate to all (neglecting Rh factor). Synonym: universal donor.
  • noun printing American Library Association Abbreviation of octavo, a book size (20-25 cm).
  • noun soccer Someone associated with Leyton Orient Football Club, as a player, coach, supporter etc.
  • noun The ordinal number fifteenth, derived from this letter of the English alphabet, called o and written in the Latin script.
  • preposition grammar The English vocative particle (always in upper case), used for direct address in translations from languages which have the vocative case.
  • interjection Expression of earnestness or reverence, used before the name of a deity or revered person in impassioned speech.


from Wiktionary, Creative Commons Attribution/Share-Alike License

Old Saxon gloss o (950s) in Lambeth ms. (957) of Gallican Psalter and ó, o (>1000) in Durham Hymns, regularly as redundant "o eala þu" and "ó eala þu" at uppercase proper names in paraphrase and some verbs in periphrase; Anglo-Norman O (~1200) in mss. of Sts. Juliana and Katherine, and other religiose writs; and English O, o (~1525) in The New Testament Translation by William Tyndale for Ancient Greek , Latin o (vocative, intensive: Old English èalà, æàlà, ǽlà, hèlà; also Middle English O (Actus 13:10; Romayns 9:20; Galaþies 3:1), ò (Romayns 2:1,3), Irish a (Maþeu 15:28;17:17; Luk 9:41;24:25; Actus 13:10) or A (Actus 27:21; Romayns 11:33)—sometimes mistranscribed as O in online bibles—, þou (1Tymoþe 6:20), ȝe (Actus 18:14), or (Actus 1:1; Ebrews 10:7) in Newe Testament by Iohn Wiclif (1382). intensive, interrogative: Old English ; English lo, oh (1534))


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