The document discusses the principles of design that are important for costume designers to understand, including repetition, gradation, radiation, dominance, harmony, contrast, proportion, balance, rhythm, and unity. It notes that repetition, gradation, radiation, and rhythm create movement and direction in a design, while radiation, dominance, and contrast are used to draw attention and create focal points. Successful designs incorporate repetition, gradation, harmony, balance, and unity to bring design details together cohesively.