Fourth

Part of speech: noun (n.)

1. 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.

2. The interval of two tones and a semitone, embracing four diatonic degrees of the scale; the subdominant of any key. The Fourth, specifically, un the United States, the fourth day of July, the anniversary of the declaration of American independence; as, to celebrate the Fourth.

Part of speech: adjective (a.)

1. Next in order after the third; the ordinal of four.

2. Forming one of four equal parts into which anything may be divided.