可能补语

Take any verb-result pair from the resultative complement page, insert 得 (de) for "manage to" or 不 (bu) for "fail to," and the pair stops reporting an outcome and starts assessing whether one is achievable. The mechanics are strict: the infix goes between verb and result (听得懂, never a 能 in sight), the question form offers both poles (你听得懂听不懂?) or adds 吗 (听得懂吗?), and the whole thing stays one phonological word, the 得/不 unstressed and quick.

In practice the pattern lives in the negative. Corpus counts and classroom experience agree: 听不懂, 看不见, 睡不着, and 买不起 are everyday speech, while their positive twins appear mostly in questions and contradictions (你不是听不懂，是不想听, "it's not that you can't understand, you don't want to"). The negative forms encode life's frictions so compactly that each is effectively a word: 吃不下 (no more room), 想不起来 (can't call it to mind), 说不出来 (can't put it into words), 离不开 (can't do without).

Several everyday words are potential complements that fossilized so completely that learners use them for years before noticing. 对不起 (duìbuqǐ), "sorry," is 对 (face someone) + 不起: I cannot face you. Its dignified twin 对得起 survives in full productivity: 要对得起父母, be worthy of your parents' sacrifices. 来不及 (láibují), "no time left," is arrive + not + reach: the deadline outran you; 来得及 reassures that time remains. 受不了 (shòubuliǎo), "unbearable," uses the liǎo reading of 了 as the complement of possibility: cannot endure it, the summer humidity's official review. 怪不得 (guàibude), "no wonder," is literally "cannot blame": once the reason appears, blame has nowhere to land.

The affordability set deserves its own mention because 起 ("manage to rise under the weight of") prices anything: 买不起 (can't afford to buy), 吃不起 (can't afford to eat, said of surging fruit prices), 住不起 (can't afford to live there), 惹不起 (can't afford to provoke, the standard verdict on fearsome bosses and toddlers). The pattern is productive enough that internet Chinese coins new ones on demand; whatever inflation touches next will be X不起 within the week.

English "can" covers both permission and achievability, so learners reach for 能 everywhere and produce grammatical but unnatural sentences like 我不能听懂. The division of labor: 能 (and 可以) handle permission, circumstance, and general capacity (这里不能停车, no parking here; 他病了，不能来, he's ill and can't come). The potential complement handles whether a specific action can reach its specific result: 字太小，我看不清楚 (the print's too small, I can't make it out). When both are possible, the potential form is what natives say. One reliable tell: if the English "can't" is followed by a verb of outcome (understand, find, finish, afford, catch), Chinese wants the infix, not 能.

The formal written register does allow 能 + verb-result (未能找到, "was unable to locate," in reports and apologetic emails), which is why learners meet both. But in speech the potential complement carries the load, and mastering its negatives upgrades listening comprehension immediately, since natives use them constantly and contract them fast: tīngbudǒng arrives as three quick syllables with the middle one nearly swallowed.