O, ooʊ(n.)(pl.)O's; Os, o's; os; oes.

1. the 15th letter of the English alphabet, a vowel.

2. any spoken sound represented by this letter.

3. something shaped like anO.

4. a written or printed representation of the letter O or

   o.

Ooʊ(interj.; n.)(pl.)O's.

1. (interj.)(used before a name in direct address, esp. in solemn or poetic language, to lend earnestness to an appeal):

   Hear, O Israel!

2. (used as an expression of surprise, pain, annoyance, longing, gladness, etc.)

3. (n.)the exclamation “O.”

Origin of O:

1125–75; ME < OF < L ō

O

1. Old.

2. Gram. object.

   Category: Grammar

O^*

1. the 15th in order or in a series.

2. the Arabic numeral; zero; cipher.

3. a major blood group.

   Category: Physiology

   Ref: Compare ABO system.

4. oxygen.

   Category: Chemistry

^* Symbol..

o'(prep.)

1. of:

   o'clock; will-o'-the-wisp.

2. Chiefly Dial. on.

Origin of o':

ME; by shortening.

O'

1. a prefix meaning “descendant,” in Irish family names:

   O'Brien; O'Connor.

   Category: Affix

Origin of O':

repr. Ir ó descendant, OIr au

o-

1. ortho-.

   Category: Chemistry, Affix

o-

1. var. of ob- before

   m: omission.

   Category: Affix

o-

1. var. of oo- :

   oidium.

   Category: Affix

-o-

1. the typical ending of the first element of compounds of Greek origin, used regularly in forming new compounds with elements of Greek origin and often used in English as a connective irrespective of etymology: Franco-Italian; geography; seriocomic; speedometer.

   Category: Affix

   Ref: Compare -i-. 8

Origin of -o-:

ME (< OF) < L < Gk

-o

1. a suffix occurring as the final element in informal shortenings of nouns (ammo; combo; promo); -o also forms nouns, usu. derogatory, for persons or things exemplifying or associated with that specified by the base noun or adjective (pinko; weirdo; wino).

   Category: Affix

2. a suffix occurring in informal noun or adjective derivatives, usu. grammatically isolated, as in address:

   kiddo; neato; righto.

   Category: Affix

O.

1. pint.

   Category: Weights and Measures

2. October.

3. Ohio.

Origin of O.:

< L octārius

o.

1. ocean.

2. pint.

   Category: Weights and Measures

3. octavo.

4. off.

5. old.

6. only.

7. order.

8. out.

   Category: Sport

Origin of o.:

< L octārius