The ordinal number fifteenth, derived from this letter of the English alphabet, called o and written in the Latin script.

The fifteenth letter of the English alphabet, called o and written in the Latin script.

(medicine) Initialism of alert and oriented.

(stenoscript) (a) an initial letter ⟨o⟩

The name of the Latin-script letter O. / A zero (used in reading out numbers).

Over

A blood type that has no antigens. It lacks the A, B and Rh factors on the blood cells. It is the universal donor for blood and can give blood to any blood type, but can only receive O- blood.

(organic chemistry) ortho-

Added to verb stems to create a noun describing an error relating to the action described by the verb.

A colloquializing suffix, typically appended to names, abbreviations of long words, or substantive uses of adjectives.