in Western music, the smallest distance from one note to the next (for example, on the piano), or the distance from one swarastaana to the next. s to r1, r1 to r2, m1 to m2, etc. are all half-steps. Two half-steps are equivalent to a whole-step. Half steps in Western notes are, for example, from B to C or from E to F
The smallest distance between two notes (in Western music). Sometimes called a "chromatic step" or "semitone". On a piano, notes are one half-step apart. On a guitar, frets are one half-step apart. There are 12 half-steps (and notes) in an octave.