Secondary leading-tone chord

In music theory, a secondary leading-tone chord or secondary diminished seventh, as in seventh scale degree or leading-tone, is a secondary chord but rather than being a dominant it is a leading-tone seventh chord or triad, which are similar in function to dominant chords. Also similar to secondary dominant chords they are altered chords. In contrast to secondary dominant chords they do not move in circle progressions but rather resolve up by half step. Fully diminished seventh chords are more common than half-diminished seventh chords and one may also find diminished triads [without sevenths].