The term 'WORKOUT UNITS' can be broken down into two parts: REPS (4 letters) and sets (6 letters). REPS stands for repetitions, which are the number of times a particular exercise is performed. Sets refer to the number of groups of repetitions that are done in a row. Together, reps and sets form the basis of most workout routines, as they allow for the tracking of progress and the ability to adjust the intensity of a workout.