不断 (bù duàn) means 'continuously, constantly', emphasizing that an action or change never stops. Unlike 一直 (yī zhí), which describes a state ongoing from a point in time, 不断 stresses the lack of interruption in a process. 连续 (lián xù) is used for events in a row, like consecutive days, while 不断 can be used with any verb to mean 'keep doing'.