规矩 (guī ju) has both noun and adjective senses. As a noun it means a social rule or standard of proper behavior — broader than 风俗 (fēng sú ‘social custom of a region’). As an adjective it describes someone well-behaved and proper, differing from 乖 (guāi), which implies childlike obedience of a child or pet. The word originates from the tools for drawing circles and squares, emphasizing correctness and order.