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the fifteenth letter and fourth vowel of our alphabet, its sound intermediate between a and u--with three values in English, the name-sound heard in note, the shorter sound heard in not, and the neutral vowel heard in son: as a numeral, 'nothing,' or 'zero' (formerly O=11, and ([=O])=11,000): (chem.) the symbol of oxygen: anything round or nearly so (pl. O'S, OES, pron. [=o]z).

OH, [=o], interj. an exclamation of wonder, pain, desire, fear, &c. The form oh is the more usual in prose.--O HONE! OCH HONE! an Irish exclamation of lamentation. [A.S. eá.]

Symbol of oxygen; abbreviation for oculus, eye; octarius, pint; opening.

Chemical symbol for the element oxygen.

In chemistry an abbreviation for ortho-.

the fifteenth letter and the fourth vowel in the English alphabet, has several different sounds ; a long sound, as in bone, tone; a short sound, as in lot, cot; a subdued sound, as in move (moov), prove (proov), and this last sound contracted, as in foot (foot), loot (loot). As a numeral, O stands for 11, and with a dash over it 11000. It is also the usual character for a cipher or nought. As an abbreviation it stands for old.