What Is an Interval?

An interval is the distance between two notes. Each one has a number (second, third, fourth…) counted from letter names, and a quality (major, minor, perfect, diminished, augmented) that pins down the exact half-step count. A major third is four half steps; a perfect fifth is seven.

Why intervals are the atoms of music

Chords and scales aren't collections of note names — they're collections of intervals from a root. A major triad is always root + major third + perfect fifth, whether it's C major or F♯ major. Learn the interval recipe once and you know every key. This is also why scale degrees beat note names for thinking about music.

Intervals on guitar are shapes

The guitar's superpower: an interval between two strings is a fixed physical shape you can move anywhere. A perfect fifth from the low E string is always "one string up, two frets up." Every interval has one shape for most string pairs and a one-fret adjustment across the B string. The complete visual map is in Interval Shapes on the Fretboard, and the beginner-level walkthrough is Guitar Intervals Explained.

Related terms

• Unison, minor third, major third, perfect fourth, perfect fifth, tritone, octave
• Consonance & dissonance — how intervals feel
• Songs to remember intervals — ear-training anchors