Possible Definitions:
1. Progression (n.) The act of moving forward; a proceeding in a course; motion onward.
2. Progression (n.) Course; passage; lapse or process of time.
3. Progression (n.) Regular or proportional advance in increase or decrease of numbers; continued proportion, arithmetical, geometrical, or harmonic.
4. Progression (n.) A regular succession of tones or chords; the movement of the parts in harmony; the order of the modulations in a piece from key to key.
