In music, the distance between one note and another with double or half its frequency, often heard as the same note higher or lower.
From Latin "octava (pars)" meaning "eighth (part)," from "octo" (eight). It referred to the eighth note in a scale, counting both ends.
An octave sounds like the "same" note because our ears group pitches that are double or half in frequency. You can think of each octave as a new floor in a musical building—different height, same layout.
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