To improvise well, you need to understand what you are playing and be able to transfer anything you hear in your mind to the fretboard. To do this, you need a system for identifying pitches that can be applied to any scale in any key. Scale degrees are used to identify a note’s position in the scale in relation to the root note or key note (the note after which the key is named – also called the tonic).
Here are the notes of the C major scale with the scale degrees written under the notes. Try playing the scale and singing the scale degree as you play. It is important to learn scale degrees well for two reasons: they are essential for transposing music to other keys, a skill that will make you more versatile in a band; and they will help you play more effectively over chord progressions.