half-step

/HH AE1 F S T EH1 P/
noun
  1. 1

    An interval of which there are seven in a fifth or twelve in an octave, consisting of two tones whose frequency ratio is about 1.059 or 18/17.

Synonyms

Source: https://en.wiktionary.org/wiki/half%20step, https://en.wiktionary.org/wiki/half-step