Next in order after the third; the ordinal of four.
- The ordinal number matching the number four in a series.
- One of four equal parts.
- Music A tone four degrees above or below a given tone in a diatonic scale.
- Music The interval between two such tones.
- Music The harmonic combination of these tones.
- Music The subdominant of a scale or key.
- The transmission gear or gear ratio used to produce forward speeds next higher to those of third in a motor vehicle.
- The Fourth of July; Independence Day. Used with the: went to a parade on the Fourth.