Definitions of fourth:
- noun: the musical interval between one note and another four notes away from it
- noun: following the third position; number four in a countable series
- noun: one of four equal parts
- adjective: coming next after the third and just before the fifth in position or time or degree or magnitude
- adverb: in the fourth place
Example: "Fourthly, you must pay the rent on the first of the month"