时间

时间 (shíjiān) is the abstract noun 'time' — duration, the resource you spend, the concept itself. It is the word you use to say you have time, are short on time, or need time: 我有时间 ('I have time'), 没时间 ('no time'), 时间不够 ('not enough time'). It covers both 'how long' (duration) and 'when' (a point on the clock or calendar), but for clock time English-speakers should note: to ask 'what time is it,' Chinese normally uses 几点 (jǐ diǎn, 'what o'clock'), not 什么时间.

时间 also doesn't take 个 as a measure word the way English-speakers might expect; use 段 (duàn) for a stretch of time or 点 (diǎn) for a small amount. Related but distinct: 时候