Often, intervals are annotated using abbreviations. Abbreviations for intervals consist of a single letter in uppercase or lowercase that corresponds to the interval quality and a number which corresponds to the interval number. For instance, a perfect fifth is annotated as P5 where the uppercase letter P corresponds to "perfect" and the number 5 corresponds to "fifth".
The following shows the uppercase and lowercase letters that are used when annotating intervals:
P = perfect interval quality
d = diminished interval quality
A = augmented interval quality
m = minor interval quality
M = major interval quality
The following shows the numbers that are used when annotating intervals:
1 = prime
2 = second
3 = third
4 = fourth
5 = fifth
6 = sixth
7 = seventh
8 = octave