能 / 会 / 可以 — picking the right 'can'
English 'can' is a single bucket — 'I can swim', 'I can come tomorrow', 'May I come in?'. Mandarin splits this into three different verbs, and choosing the wrong one is one of the most common beginner mistakes. 能 néng is for circumstantial possibility — whether the situation lets you do it. 会 huì is for learned skills — things you trained for, plus likelihood about the future. 可以 kěyǐ is for permission — asking or granting it. All three sit BEFORE the main verb, none of them conjugate, and all three negate with 不. The trick is matching the right flavor to the situation.
能 — circumstantial 'can / be able to'
Use 能 when the question is whether circumstances allow the action right now: time, energy, health, schedule, physical ability. 我今天不能来。 = I can't come today (something's stopping me). 你能听见我吗? = Can you hear me? (a hearing question, not a skill). 她能吃辣的。 = She can handle spicy food (her body tolerates it). 我太累了,不能去。 = I'm too tired, I can't go. The pattern is subject + 能 + verb (+ object). 能 is also the right word when the question is about capacity (这个杯子能装一升水 = this cup can hold a liter of water).
会 — learned skill + future likelihood
会 is for things you LEARNED how to do — languages, instruments, sports, driving. 我会说中文。 = I can speak Chinese (I trained for it). 她会开车。 = She knows how to drive. 你会做饭吗? = Can you cook? 我不会游泳。 = I can't swim (never learned). The second job of 会 is future likelihood — 'will / is likely to'. 明天会下雨。 = It'll rain tomorrow. 她会来。 = She'll come / She's likely to come. So 'I can speak Chinese' is 我会说中文 — never 我能说中文 (which would suggest the room is letting you speak Chinese right now).
可以 — permission
可以 is the politeness word — asking permission or granting it. 我可以进来吗? = May I come in? 你可以走了。 = You may go (now). 学生不可以在这里吃饭。 = Students aren't allowed to eat here. The pattern is the same — 可以 + verb. To say 'no, you can't' as a refusal of permission, 不可以 is sharper than 不能. In real life, 可以 and 能 overlap a lot for asking favors: 可以帮我吗? and 能帮我吗? both mean 'can you help me?' (the second sounds slightly more about capacity, the first about willingness).
Picking the right one — three quick tests
Ask: (1) Is it a SKILL I trained for? → 会. (2) Is it about whether the SITUATION allows it (time, energy, physical ability)? → 能. (3) Am I asking or giving PERMISSION? → 可以. Examples: 'I can drive' (skill) → 我会开车. 'I can drive you to the airport' (situation/willingness) → 我能开车送你. 'You may drive my car' (permission) → 你可以开我的车. The same English 'can drive' becomes three different sentences. Get this wrong and you'll still be understood, but native speakers will hear the off-note immediately.
Questions and negation
All three work in both question patterns from earlier lessons. 吗 version: 你会说中文吗? verb-not-verb: 你会不会说中文? 能不能? 可不可以? are all natural. Negation goes right before the modal: 不能, 不会, 不可以. Note: 不会 for a learned skill is permanent ('I don't know how to'); 不能 is situational ('I can't right now'). 我不能来 = I can't come (today, this time). 我不会来 would mean 'I won't come' — about future likelihood, not skill — so be careful, 不会 + verb often shades into 'won't'.
