A "perfect fifth" is a musical interval that spans five diatonic scale degrees. It is formed by taking the first note of a scale and counting up five notes, including the starting note. For example, in the C major scale, the perfect fifth above C is G. This interval is known for its consonant and harmonious sound. In Western music, perfect fifths are fundamental in creating chords and melodies. They are often used in triads, which consist of three notes, and are essential in establishing the tonality of a piece. The perfect fifth is considered one of the most stable and pleasing intervals in music theory.