结果补语
jiéguǒ bǔyǔChinese verbs describe the attempt; a second syllable reports the outcome. Listening is 听, but understanding what you heard is 听懂.
English verbs quietly bundle outcomes: "find" means your search succeeded, "see" means light reached your understanding. Chinese unbundles them. The bare verb names the activity, and a 结果补语 (resultative complement), welded on directly after, names what came of it. 找 (zhǎo) is to search; 找到 (zhǎodào) is to search-and-attain: to find. 听 is to listen; 听见 is to hear; 听懂 is to understand what you heard. The sentence 我找了半天，可是没找到 ("I looked for ages but didn't find it") is impossible to translate word-for-word into English precisely because English cannot say "find" without the success built in.
This is the grammatical machine behind pairs a learner otherwise memorizes blindly: 看 (look) versus 看见 (see), 学 (study) versus 学会 (master), 买 (shop for) versus 买到 (get one's hands on). The complement slot takes verbs (见, 懂, 会) and adjectives (好, 错, 干净) alike, and the two syllables behave as one verb: aspect 了 follows the whole unit (吃完了饭), never splits it.
到 dào (attained) → 找到 find ; 买到 manage to buy ; 收到 receive ; 想到 think of
见 jiàn (perceived) → 看见 see ; 听见 hear ; 闻见 smell
懂 dǒng (understood) → 听懂 follow (speech) ; 看懂 follow (text)
好 hǎo (done properly) → 准备好 be ready ; 修好 fix ; 坐好 sit properly
错 cuò (wrongly) → 说错 misspeak ; 写错 miswrite ; 认错人 mistake someone's identity
A dozen complements do most of the work, and each has a personality worth knowing. 完 is pure completion and combines with almost anything consumable or performable. 到 marks attainment of a target and also extends to reaching places and times (走到学校, walk as far as school; 等到十点, wait until ten). 见 is perception registering, which is why 看见 and 听见 pair with the senses. 好 means the action reached a satisfactory, usable state: 饭做好了 announces dinner is ready, and a parent's 坐好! orders the wriggling child into proper position. 错 and its opposite 对 grade the outcome: 猜对了 (guessed right). Two more earn early adoption: 会 (mastery: 学会游泳, learn to swim, as opposed to merely studying it) and 开 (apart/open: 打开 open up, 分开 separate).
Because a result either obtained or it did not, negation uses 没 (the realized-action negator) before the whole verb-result unit: 我没听懂 (I didn't understand), 作业还没做完 (the homework isn't finished yet). Putting 不 there is the classic learner error; 不 belongs to habitual or hypothetical statements and, crucially, to the potential form (听不懂, "unable to understand"), which this guide treats on its own page. The near-minimal pair is worth staring at once: 没听懂 reports a failure that happened; 听不懂 reports an inability.
Resultatives also explain why the 把 construction exists. 把 fronts the object so the verb-plus-result can land on it as a verdict: 把作业做完 (get the homework done), 把门关好 (shut the door properly), 把字写错了 (wrote the character wrong). A 把 sentence without some complement or other elaboration after the verb feels amputated to native ears, and the resultative is the most common thing that fills the slot; the two patterns are roommates, and this guide's 把 page holds the lease.