# Diminished triad
A diminished triad is a three-note chord built from two stacked minor thirds, so that it contains a minor third and a diminished fifth above its root. It is one of the four triad qualities of tonal harmony, alongside major, minor, and augmented, and its diminished fifth (also called a tritone) gives the chord its characteristically tense, unstable sound that seeks resolution.
| Key fact | Detail |
|---|---|
| Construction | Two stacked minor thirds: a minor third between root and third, and another minor third between third and fifth[1](https://open.lib.umn.edu/musiccomposition/chapter/common-practice-era-chord-qualities/) |
| Intervals above the root | Root, minor third, diminished fifth; the diminished fifth spans six semitones (a tritone)[2](https://fiveable.me/ap-music-theory/key-terms/diminished-triad) |
| Examples | B–D–F is a B diminished triad; C–E♭–G♭ is a C diminished triad |
| Relation to minor triad | A minor triad with its fifth lowered by one semitone[3](https://schoolofguitar.com/images/theory.pdf) |
| Analytical label | Lowercase root followed by a small zero (degree sign), as in vii°; chord symbols use *dim* or a degree sign[1](https://open.lib.umn.edu/musiccomposition/chapter/common-practice-era-chord-qualities/) |
| Diatonic locations | On scale degree 7 (vii°) in a major key; on scale degree 2 (ii°) in natural minor[2](https://fiveable.me/ap-music-theory/key-terms/diminished-triad) |
| Seventh-chord offspring | It is the base of both the half-diminished seventh chord (1 ♭3 ♭5 ♭7) and the fully diminished seventh chord (1 ♭3 ♭5 ♭♭7)[2](https://fiveable.me/ap-music-theory/key-terms/diminished-triad) • [4](https://www.jazzguitar.be/blog/diminished-chords/) |
## Construction and interval structure
A triad is a chord of three distinct pitches stacked in thirds. The quality of a triad depends on the sizes of its two stacked thirds: major plus minor gives a major triad, minor plus major gives a minor triad, minor plus minor gives a diminished triad, and major plus major gives an augmented triad[5](https://viva.pressbooks.pub/openmusictheory/chapter/augmented-options/). In the diminished triad, the two minor thirds (three semitones each) add up to a diminished fifth of six semitones between root and fifth[6](https://www.opentextbooks.org.hk/system/files/export/2/2180/pdf/Understanding_Basic_Music_Theory_2180.pdf). This is the interval the chord is named for: where major and minor triads contain a perfect fifth, the strong consonance that stabilizes them, the diminished triad instead contains a diminished fifth[1](https://open.lib.umn.edu/musiccomposition/chapter/common-practice-era-chord-qualities/).
A quick way to hear the difference from a minor triad: both have a minor third above the root, but the minor triad's fifth is perfect, and that single added semitone of tension is the giveaway of the diminished quality[2](https://fiveable.me/ap-music-theory/key-terms/diminished-triad).
**Terminology.** The label "three-note chord" refers to three different pitch classes among the chord's members, rather than to precisely three attacks being sounded; a texture written in four parts may double a single member and yet still present a diminished triad. Inversion changes which chord member lies in the bass, not the root or the quality[10](https://www.clementstheory.com/study/inverting-triads/).
## Occurrence in keys and harmonic function
Diatonic diminished triads appear at predictable places. Stacking thirds on each degree of a major scale produces three major triads, three minor triads, and one diminished triad on the leading tone[7](https://www.realmusictheory.com/learn/triads). In natural minor, the diminished triad falls on scale degree 2[2](https://fiveable.me/ap-music-theory/key-terms/diminished-triad).
Function follows context rather than the label alone. In common-practice harmony the diminished triad matters chiefly in its dominant-family role, as the leading-tone chord vii° and as the upper structure of the [dominant seventh chord](https://www.edgepedia.org/dominant-seventh-chord) (V⁷ contains the diminished triad built on its third)[5](https://viva.pressbooks.pub/openmusictheory/chapter/augmented-options/). In natural minor, the ii° triad more often serves a predominant role, frequently in first inversion, and raising scale degree 7 in minor produces a leading-tone diminished triad[11](https://human.libretexts.org/Courses/Sierra_College/Equipping_the_Musical_Ear/21%3A_Diminished_Chords/21.05%3A_Diminished_Chords_in_Major_and_Minor_Keys).
**Relative frequency.** In tonal music, triads of major and minor quality occur most often; diminished triads appear less frequently, and augmented triads are the least common of all.[8](https://pressbooks.macalester.digital/multimodalmusicianship/chapter/triads/) The diminished triad is nonetheless central to tonal harmony, especially in its dominant function as vii° and as part of V⁷[5](https://viva.pressbooks.pub/openmusictheory/chapter/augmented-options/).
## Seventh chords built on the diminished triad
Adding a diatonic seventh above the diminished triad produces the two diminished-type seventh chords. The [half-diminished seventh chord](https://www.edgepedia.org/half-diminished-seventh-chord) adds a minor seventh (formula 1 ♭3 ♭5 ♭7), while the fully diminished seventh chord adds a diminished seventh (1 ♭3 ♭5 ♭♭7), a semitone lower[4](https://www.jazzguitar.be/blog/diminished-chords/). Because the fully diminished seventh chord stacks only minor thirds, its inversions share one shape and any of its notes can serve as the root, a property the three-note triad does not share, since the diminished triad's intervals (3, 3, 6 semitones around the circle) are not all equal[4](https://www.jazzguitar.be/blog/diminished-chords/). Diminished chords are an important part of the jazz guitarist's harmonic palette, and in classical music diminished triads serve as expressive devices for modulation and emotional expression[4](https://www.jazzguitar.be/blog/diminished-chords/) • [9](https://themusictheoryprofessor.com/article/exploring-diminished-triads-construction-and-use-in-classical-and-jazz-music).
## Notation and chord symbols
In Roman-numeral analysis, the diminished quality is marked by a lowercase numeral with a degree sign (°), as in vii° or ii°[1](https://open.lib.umn.edu/musiccomposition/chapter/common-practice-era-chord-qualities/) • [7](https://www.realmusictheory.com/learn/triads).
## References
1. [Common Practice Era Chord Qualities, Music Composition & Theory (University of Minnesota, open textbook)](https://open.lib.umn.edu/musiccomposition/chapter/common-practice-era-chord-qualities/)
2. [Diminished Triad, AP Music Theory Definition & Guide, Fiveable](https://fiveable.me/ap-music-theory/key-terms/diminished-triad)
3. [Theory Primer for Guitar, School of Guitar](https://schoolofguitar.com/images/theory.pdf)
4. [Diminished Chords: Chord Chart, Applications & Examples, Jazz Guitar Online](https://www.jazzguitar.be/blog/diminished-chords/)
5. [Augmented Options, Open Music Theory](https://viva.pressbooks.pub/openmusictheory/chapter/augmented-options/)
6. [Understanding Basic Music Theory, open textbook (HKUST)](https://www.opentextbooks.org.hk/system/files/export/2/2180/pdf/Understanding_Basic_Music_Theory_2180.pdf)
7. [Triads, RealMusicTheory](https://www.realmusictheory.com/learn/triads)
8. [Triads, Multimodal Musicianship (Macalester College)](https://pressbooks.macalester.digital/multimodalmusicianship/chapter/triads/)
9. [Exploring Diminished Triads: Construction and Use in Classical and Jazz Music, The Music Theory Professor](https://themusictheoryprofessor.com/article/exploring-diminished-triads-construction-and-use-in-classical-and-jazz-music)
10. [Study: Inverting triads, Clements Theory](https://www.clementstheory.com/study/inverting-triads/)
11. [21.5: Diminished Chords in Major and Minor Keys, Humanities LibreTexts](https://human.libretexts.org/Courses/Sierra_College/Equipping_the_Musical_Ear/21%3A_Diminished_Chords/21.05%3A_Diminished_Chords_in_Major_and_Minor_Keys)
---
*Topic: Encyclopedia › Arts and culture › Music › Musical practice and theory › Instruments, theory, and world traditions › Music theory — harmony, melody, and counterpoint › Harmony and chords*
*Initially written Sep 17, 2026 · Reviewed: Sep 20, 2026; Sep 30, 2026; Oct 25, 2026 · Edited: Sep 20, 2026; Oct 11, 2026; Oct 25, 2026 · Last review: Oct 25, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license