scale

scale - noun - a collection of musical notes that provides material for part or all of a musical work.

Someone once said the most difficult thing to define is the simplest. How true of the musical scale. Not only is this a collection of notes, but it also has several properties and additional (adverbs!) to describe it (diatonic, chromatic, whole-tone, etc). Ignoring most of these additional properties doesn't really do justice to the term, but consider the following items: scales go up and/or down a musical score and the separation of the notes from each other is constant. If you'd really like to be bamboozled by the description of a scale, try out wikipedia.