离合词
líhécíWords that unzip: 见面 is to meet, but meeting him is 跟他见面 and meeting once is 见一次面, because the "word" is secretly verb plus object.
The name says it: 离合词, "separate-combine words." A large class of everyday two-syllable verbs look like single words in the dictionary but are internally verb + object: 睡觉 is sleep + a sleep, 吃饭 is eat + rice/meal, 唱歌 is sing + song, 见面 is see + face, 洗澡 is wash + bath, 结婚 is tie + marriage. Used whole, they behave like intransitive verbs: 我们明天见面 (we meet tomorrow). But the moment grammar needs a place to sit, the object half politely steps back and the machinery moves in between: 见了面 (met), 见过面 (have met before), 见个面 (meet up, casual), 睡了一觉 (had a sleep), 帮了我一个大忙 (did me a big favor).
Whether these are words or phrases is a genuine dispute in Chinese linguistics, and the honest answer is: both, which is what makes them a category. For the learner the practical rule is simpler. The dictionary lemma is a convenience; the grammar treats the two halves as verb and object, and everything else follows from that single fact.
个 (casualizer) → 见个面, 洗个澡, 帮个忙 : "grab a quick one"
duration / times → 睡了八个小时的觉 ; 见了三次面
possessive target → 生他的气 (angry at him) ; 帮我的忙 (help me)
reduplication → verb half only : 唱唱歌, 散散步 (never 唱歌唱歌)
Everything that would follow an ordinary verb slips inside the separable one
The gap's tenants are exactly the things that normally follow a verb: aspect particles, measure phrases, duration, and the beneficiary or target dressed as a possessor. That last one produces the constructions learners find most alien and natives find most natural: 生他的气, literally "generate his anger," means to be angry at him; 帮我的忙 is to help me; revenge dramas run on 报仇 splitting into 报了大仇. Duration goes inside because Chinese counts time on the object: eight hours of sleep is 八个小时的觉, a possessed sleep.
Reduplication, the softening doubling covered across this guide's grammar pages, copies only the verb half: 唱唱歌 (sing a little), 见见面 (meet briefly), 散散步 (take a stroll). And the casual 个, semantically almost empty, marks the activity as light and social: 改天见个面 ("let's grab a meet-up sometime") carries exactly the weight of its English translation, none.
The signature error is bolting a second object onto a verb that already contains one: 见面他, 结婚她, 帮忙我 are all impossible, because 面, 婚, and 忙 occupy the object seat. The repair is a preposition fronting the person: 跟他见面 (meet with him), 跟她结婚 (marry her), 跟朋友聊天 (chat with friends), with 和 or 与 as register variants of 跟. For 帮忙 the alternative repair is to abandon the 忙 and use bare 帮, which takes objects freely: 帮我 (help me), 帮我买杯咖啡 (get me a coffee).
How do you know a verb is separable before it bites you? Heuristics: if the second syllable is a noun a dictionary lists independently (觉, 饭, 歌, 澡, 婚, 气), suspicion is warranted; if you have ever heard it split (见个面), the case is closed. Textbooks mark the class with a // in pinyin (jiàn//miàn), a notation worth learning to read as a warning label. When in doubt, front the person with 跟 and no harm can follow: the workaround is always grammatical, while the bolted-on object never is.