用心 (yòng xīn) means 'attentive, diligent, careful' — it emphasizes putting effort and focus into a task, often with a sense of dedication. It is stronger than 小心 (careful to avoid danger) and 仔细 (meticulous in details), and more everyday than the formal 精心 (meticulous, done with great care). Unlike 动机 (motive, intention), 用心 as an adjective is about the quality of attention, not the reason behind an action.