Subdominant: The subdominant is the fourth scale degree of a major or minor key. It provides a sense of stability before resolving to the dominant.
Dominant seventh chord: A dominant seventh chord is built on the dominant scale degree and consists of four notes. It adds extra tension and creates a stronger desire to resolve to the tonic.
Dominant function: Dominant function refers to how chords with dominant characteristics (such as V or V7) create tension and lead to resolution within a musical piece.