An unresolved seventh is a specific characteristic of seventh chords where the dissonance created by the seventh degree is not resolved to the tonic or root of the chord, creating a feeling of tension. This unresolved quality can heighten emotional intensity and create forward motion in the music, as the listener anticipates the resolution. In voice leading, it's essential to recognize how unresolved sevenths function within harmonic progressions and contribute to the overall flow of a piece.