A diatonic interval which traverses 3 steps in a diatonic scale, and covers a pitch distance bounded by 4 nominals inclusively. This refers to the generic usage of "4th" without a qualifying adjective, which often precedes the interval name in standard diatonic usage. Thus, the various different types of diatonic 4ths are (in order of size from smallest to largest):
The use of "4th" alone, without a qualifier, generally refers specifically to the perfect-4th.
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