·adj Next in order after the third; the ordinal of four.
II. Fourth ·adj Forming one of four equal parts into which anything may be divided.
III. Fourth ·noun The interval of two tones and a semitone, embracing four diatonic degrees of the scale; the subdominant of any key.
IV. Fourth ·noun One of four equal parts into which one whole may be divided; the quotient of a unit divided by four; one coming next in order after the third.