the quality of being clearly expressed and easy to understand 表达清楚的；易懂的 to write with clarity and lucidity 写得清晰明了
the ability to think clearly, especially during or after a period of mental illness （尤指生病期间或病愈后，糊涂状态中或过后）头脑清晰的，清醒的 a rare moment of lucidity 难得的清醒时刻