idea

Scale degrees are the chords composing that scale. Chords in a scale can be noted using roman numerals from I (the root, or tonic) to VII. For example in the C major melodic scale:

Chord	C	D	E	F	G	A	B
Roman numeral	I	II	III	IV	V	VI	VII
Degree	Tonic	Supertonic	Mediant	Subdominant	Dominant	Submediant	Leading tone

Upper case numerals represent major scales. Lower case numeral represent minor scales.

references

Wikipedia / Roman numeral analysis