O

O¹

(also o)

noun (plural Os or O's)

1》 the fifteenth letter of the alphabet.

2》 denoting the next after N in a set of items, categories, etc.

3》 a human blood type (in the ABO system) lacking both the A and B antigens.

4》 (also oh) zero (in a sequence of numerals, especially when spoken).

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O²

abbreviation

1》 US Ohio.

2》 Cricket (on scorecards) over(s).

symbol the chemical element oxygen.

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O³

exclamation

1》 archaic spelling of oh¹.

2》 used before a name in the vocative.