适度 (shì dù) means 'moderate, appropriate' in terms of degree or extent, not specifically quantity. It contrasts with 适量 (shì liàng), which focuses on appropriate amount/quantity (e.g., food intake), and 中等 (zhōng děng), which means 'medium, average' in level or size. 适度 is used for avoiding extremes in behavior, exercise, speech, etc.