Twelve semitones. The notes sound like the same pitch, just higher. Complete stability.
Root on string 4, fret 0. Interval on string 4, fret 12.
The octave is one of the most expressive intervals in melody. "Somewhere Over the Rainbow" opens with the famous octave leap. In jazz, Wes Montgomery's octave technique became legendary. On guitar, octaves are used to create dense melodic lines. In an orchestra, octave doublings are the foundation of tutti sound.
Memorize the opening of "Somewhere Over the Rainbow" — it is an ascending octave. On guitar, find the octave: on the same string — 12 frets higher, or skip one string — two frets higher (on E-A-D-G strings) or three frets (G-B). Play melodies in octaves using the Wes Montgomery method.
Learn to recognize intervals by ear with the interactive trainer.