Diminished third

In classical music from Western culture, a diminished third (Play^ⓘ) is the musical interval produced by narrowing a minor third by a chromatic semitone. For instance, the interval from A to C is a minor third, three semitones wide, and both the intervals from A♯ to C, and from A to C♭ are diminished thirds, two semitones wide.

${ \override Score.TimeSignature #'stencil = ##f \relative c'' { \time 4/4 \set Score.tempoHideNote = ##t \tempo 1 = 20 <ais c>1 <a? ces> } }$

Being diminished, it is considered a dissonant interval.