Each note in a scale represents a scale degree. Scale degrees are named numerically in ascending pitch order, using roman numerals starting from whatever scale note you are using. A song can be written in any scale and in any key. That scale is considered the first mode, and all the other scale degrees will be numbered beginning from that scale. The number of degrees a scale has is equal to the number of notes in that scale. For example, the scale above has five notes and thus has five scale degrees. A 7note scale will have seven scale degrees, and so on.
