Fourth, n.
 1. One of four equal parts into which one whole may be divided; the quotient of a unit divided by four.
 2. Mus. The interval of two tones and a semitone, embracing four diatonic degrees of the scale; the subdominant of any key.
 3. One coming next in order after the third.
 The Fourth, specifically, in the United States, the fourth day of July, the anniversary of the declaration of American independence; as, to celebrate the Fourth.

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