Scales refer to a series of notes that go in an ascending and descending manner. In music theory, a scale degree is the name given to a particular note of a scale to specify its position relative to the tonic (the main note of the scale).
The tonic is considered to be the first degree of the scale, from which each octave is assumed to begin. Any musical scale may be thought to have degrees. However, the notion of scale degree is most commonly applied to scales in which a tonic is specified by definition, such as the 7-tone diatonic scales (e.g. the C-major scale C–D–E–F–G–A–B, in which C is the tonic).