Final answer:
A seventh chord is a four-note chord consisting of a triad and an additional note called the seventh. The dominant seventh chord is one specific type of seventh chord that consists of a major triad and a minor seventh. It has a strong tendency to resolve to the tonic chord.
Step-by-step explanation:
In music theory, a seventh chord is a four-note chord consisting of a triad and an additional note called the seventh. There are several types of seventh chords, including major-minor, minor-major, diminished, and augmented. The dominant seventh chord is one specific type of seventh chord that consists of a major triad and a minor seventh.
For example, in the key of C major, the dominant seventh chord would be G7, which consists of the notes G, B, D, and F. It is called dominant because it is built on the fifth scale degree of the key and has a strong tendency to resolve to the tonic chord, creating a sense of tension and resolution.