Eleventh

augmented eleventh
Inverse	diminished fifth
Name
Abbreviation	A11
Size
Semitones	18
Interval class	6
Just interval	45:16
Cents
12-Tone equal temperament	1800.0
Just intonation	1790.2

perfect eleventh
Inverse	perfect fifth
Name
Other names	Compound fourth
Abbreviation	P11
Size
Semitones	17
Interval class	1
Just interval	8:3
Cents
12-Tone equal temperament	1700.0
Just intonation	1698.0

In music theory, an eleventh is a compound interval consisting of an octave plus a fourth.

A perfect eleventh spans 17 and the augmented eleventh 18 semitones, or 10 steps in a diatonic scale.

Since there are only seven degrees in a diatonic scale, the eleventh degree is the same as the subdominant (IV).^[1] The eleventh is considered highly dissonant with the major third.

An eleventh chord is the stacking of five thirds in the span of an eleventh. In common practice tonality, it usually had subdominant function as minor eleventh chord on the second degree (supertonic) of the major scale.

^ Benward, Bruce; Saker, Marilyn (2003). Music: In Theory and Practice, Vol. I. McGraw-Hill Education. ISBN 978-0-07-294262-0.

[1] Benward, Bruce; Saker, Marilyn (2003). Music: In Theory and Practice, Vol. I. McGraw-Hill Education. ISBN 978-0-07-294262-0.

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