A succession of musical pitches arranged in order of pitch-height, generally considered as a source set of pitches for musical composition.
As examples, the typical major and minor scales are diatonic, which means that they have characteristic interval patterns of "whole-tones" and semitones, usually called "whole-steps" and "half-steps" respectively. Pentatonic scales have characteristic interval patterns of "whole-steps" and "minor 3rds", etc. Note that in this latter example the so-called "minor-3rd" is still regarded as a step.
Alternatively (but rarely), an interval other than the octave may be used as the equivalence-interval. (For some examples of these, see Monzo, A stretched-'octave' scale of Charles Ives.)
A comprehensive discussion of the definition of "scale" was begun with Yahoo tuning, message 58625.