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

Peromyscus polionotus, a nocturnal rodent in the family Cricetidae, found in the southeastern United States. / Thomasomys, a genus of rodent found in South America.

(archaic) A quarter part; one fourth. / (archaic) A loaf of bread weighing about four pounds.

(organic chemistry) The sesquiterpene hydrocarbon 4, 10-dimethyl-7-isopropylidene-cyclodeca-4, 10-diene present in the essential oil of hops