What is the structure of a dominant 7th chord?

A dominant 7th chord is structured with a major triad combined with a minor 7th. This means that it consists of the root note, major third, and perfect fifth of the chord, which together form the major triad. The seventh note is then a minor seventh above the root, which adds the necessary tension and characteristic quality of a dominant chord, typically leading to resolution in harmonic progressions.

In contrast, other chord types have different structures that do not fit the definition of a dominant 7th chord. For example, a major triad with a major 7th creates a major 7th chord, and a minor triad with a minor 7th results in a minor 7th chord. A diminished triad with a diminished 7th creates a fully diminished 7th chord, which serves a different harmonic function. Therefore, the defining characteristic of a dominant 7th chord—its combination of a major triad and a minor 7th—makes the choice clear and accurate.