fourth

(noun) following the third position; number four in a countable series.

(noun) one of four equal parts. Synonyms: one-fourth, one-quarter, quarter, fourth part, twenty-five percent, quartern. Example: "A quarter of a pound."

(noun) the musical interval between one note and another four notes away from it.

(adj) coming next after the third and just before the fifth in position or time or degree or magnitude. Synonyms: 4th, quaternary. Example: "The quaternary period of geologic time extends from the end of the tertiary period to the present."

(adv) in the fourth place. Synonyms: fourthly. Example: "Fourthly, you must pay the rent on the first of the month."