A subdominant chord is a musical chord built on the fourth degree of a scale. In the key of C major, for example, the subdominant chord is F major, which consists of the notes F, A, and C. This chord plays a crucial role in creating tension and movement within a piece of music, often leading to the dominant chord. In music theory, the subdominant is often represented by the Roman numeral IV. It serves as a transition point, connecting the tonic (I) and dominant (V) chords. This relationship helps establish a sense of progression and resolution in various musical compositions.