A diminished fifth is a musical interval that spans six half steps, or semitones. It is often described as an unsettling or dissonant sound, making it a popular choice in various music genres, especially in classical and jazz. This interval can also be referred to as an augmented fourth, depending on the context in which it is used. In terms of notation, if you start on a note, such as C, the diminished fifth above it would be G♭. This interval plays a significant role in creating tension and resolution in music, often leading to a more stable consonant interval, such as a perfect fifth.