(1):
(a.) Forming one of four equal parts into which anything may be divided.
(2):
(n.) 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.
(3):
(n.) The interval of two tones and a semitone, embracing four diatonic degrees of the scale; the subdominant of any key.
(4):
(a.) Next in order after the third; the ordinal of four.