śruti, (Sanskrit: “heard”), in the music of India and Pakistan, the smallest tonal interval that can be perceived. The octave, in Indian theory, is divided into 22 śrutis. The division is not precisely equal, but these microtonal units may be compared to Western quarter tones, of which there are 24 to an octave.
The word śruti is used both to indicate a specific note and as a unit of measurement to describe the size of an interval encompassed by two given notes.