I am confused about the 了 in the sentence:


Zhèɡe biǎo kuàile wǔ fēnzhōnɡ.

This watch is running five minutes faster.

Clearly there is no change of state. Is it for completion? I don't understand what is completed...

  • Now I'm thinking it could indeed imply a change of state: the watch initially was "running fine", but then changed to "running five minutes faster".
    – Puco4
    Commented Jun 26, 2020 at 23:26
  • To me, many 了 are just expletives, not actually needed and not adding any information or meaning to the sentence. I can't tell the difference between 这个表快了五分钟 and 这个表快五分钟.
    – joehua
    Commented Jun 27, 2020 at 14:48
  • The OP's confusion just like me as to the English present tense and present perfect tense. You could just think this sentence without 了 is the present, and with 了 is present perfect. 题主的困惑就像我对之于英语的一般现在时和现在完成时一样(有时搞不清楚区别)。就这句而言,你就把没"了"的当成一般现在时,有"了"的当成现在完成时,就行了。
    – Zhang
    Commented Jul 2, 2020 at 2:59

6 Answers 6


Grammatically, the completion is not only for verbs but also for adjectives. In your example 快了, 快 is an adj. Another example might be easier to understand. 苹果红了, apples turned red. 苹果熟了 is a similar example.

Here is the dictionary definition about this usage of 了.

了 / le /


(用在动词形容词后, 表示动作或变化已经完成):

read twice;


Apples got red.


And the official 新华字典 has the similar definition:


  1. 放在动词或形容词后,表示动作变化已经完成: 买~一本书 | 水位低~一米。
  • 苹果(转)红了 - the verb 转 (turn) is implied; 苹果(成)熟了 - 成熟/ 熟 (ripen) is a verb,
    – Tang Ho
    Commented Jun 26, 2020 at 22:22
  • Another example, 飽 is an adjective in 我很飽 (I am full); But it is a verb in 我(吃)飽了, with 吃 implied
    – Tang Ho
    Commented Jun 26, 2020 at 22:28
  • 1
    @TangHo According to my dictionary, 熟 or 成熟 is indicated as an adjective. 苹果红了 doesn't necessarily mean 苹果转红了. In fact, when we say 苹果红了,we don't really care about the action but just the current state.
    – dan
    Commented Jun 26, 2020 at 23:51
  • ok. I shouldn't say "成熟/ 熟 (ripen) is a verb" ; I meant when there's a 了 after the adjective, a verb is implied. e.g. 苹果(长)熟了, 苹果(转)红了, 我(吃)飽了. if we only care about the current state, we would say 苹果红, 青豆绿
    – Tang Ho
    Commented Jun 27, 2020 at 0:08
  • 他很聪明 = he is smart ; 他聪明了 = 他(变)聪明了 = he has became smart
    – Tang Ho
    Commented Jun 27, 2020 at 0:14

It is a well-known fact in Chinese linguistics that adjectives denoting gradable attributes must be “initiated” with a certain value of degree when used in predicative constructions. In this case, we have a certain form of comparison, kind of “quite/rather X”. For example:

  1. 她很瘦 。She is (rather) slim. ??她瘦
  2. 这辆车很快。 This car is (rather) fast. ??这辆车快
  3. 这个女孩真漂亮。 This girl is really pretty. ??这个女孩漂亮

Usually, the adverb很 is used to indicate a default positive value of degree.

When the verbal suffix了 is used in a predicative construction with this kind adjectives, we also have a certain form of comparison, kind of “getting more X”. For example:

  1. 她瘦了。She is getting slimmer.
  2. 你的手表快了一点点。Your watch is getting a bit faster.
  3. 你的孩子高了。Your kid is getting taller.
  4. 几个月没见她,她好像漂亮了很多。I haven’t seen her for a couple of months. She looks much prettier.

In this case, the verbal suffix了also indicates a positive value of degree, which comes with an aspectual dimension (i.e. “getting” more X).

  • @KKTse. So, in answer to OP's question, the suffix了 in this particular case / context is not to indicate a "completed action", but to indicate "a positive, (change in), value of degree", i.e. the watch is just "getting more" fast? Commented Jun 27, 2020 at 4:15
  • This might be a better way to understand the usage of 了 for English speakers.
    – dan
    Commented Jun 27, 2020 at 4:32
  • Let me give an example to explain why people think [adjective + 了] is a thing: 紅 can be noun or adjective , but with the aspect marker了, '紅了' (became red) acting like a verb -- '紅了' = (變)紅了 . Since the verb 變 is strongly implied, it is often omitted, and that created an impression that 了 can be added not only after a verb, but it can also added after an adjective. The truth is, '了' in '紅了' is still a verb particle that serves as a result complement of the implied verb '變'
    – Tang Ho
    Commented Jun 27, 2020 at 8:00
  • 1
    @dan I am convinced the dictionary is not wrong to state 了 can be an adverb for adjective ( But 了 as an verb particle that act as a result complement of an implied verb is still a legitimate way to use it) , edited my answer
    – Tang Ho
    Commented Jun 27, 2020 at 9:01
  • 1
    @KK_Tse I'd say 荔枝红了很久了 and 荔枝熟了很久了. Without the last 了, the sentence sounds incomplete. And 我吃饱饭很久了 sounds stilted. we usually say 我早就吃饱了 for this context.
    – dan
    Commented Jun 27, 2020 at 10:24

Edit 2:

From my expert friend:

Adjectives behave very much like verbs in Chinese grammar. Like verbs, many adjectives can take aspect markers (瘦咗, 靚過), resultative particles (開心翻, 污糟晒), objects (好熟佢, 緊張啲仔女, 嬲爆佢啲同學). That’s why some grammarians call those adjectives as adjectival verbs. But they are still adjectives, and do not imply any omission of verbs before them. We think of a possible omission only because of the English grammar in the English translation (e.g. become, turn).

快了 in 这个表快了五分钟 is apparently an "adjectival verb" (adjectival + aspect marker). It is an adjective, but acts like a verb



After some consideration, I decided treating [adjective +了 ] the same as [(implied verb) + adjective + 了] . is one way to see it, but 了 does work with adjective, not as a verb particle but as an adverb 快= fast; 快了 = got faster.

"这个表[快了]五分钟" = "This watch [got faster] by five minutes "

Above is the answer with the assumption of 了 is an adverb for the adjective

Below is the answer with the assumption of 了 is a verb particle for an implied verb

Is it for completion.

手錶快了 can mean '手錶走快了' or '手錶被調快(調早)了'

If the watch is running faster than the normal speed:

  • (走快)五分钟 = (run) five minutes (faster) -- No indication of the verb (走快) is a completed action. e.g. 一小時後手錶會走快五分钟 (走快 is not a completed action here)

  • (走快了)五分钟 = (have ran) five minutes (faster) -- 了 indicates the verb (走快) is a completed action

If the watch is running at normal speed, but is five minutes ahead of the real time, it must had been set wrong:

  • (被調快)五分钟 = (be set) five minutes (ahead) -- No indication of the verb (調快) is a completed action. e.g. 明天把手錶調快五分钟 (調快 is not completed action here)

  • (被調快了) 五分钟 = (had been set) five minutes (ahead) -- 了 indicates the verb (調快) is a completed action.

  • If the clock runs 5 minutes faster now, it will continue to do so in the future. How can this be a completed action?
    – Puco4
    Commented Jun 26, 2020 at 19:51
  • 1
    The clock had finished running faster for 5 minutes. If it keep running faster than normal, it might be ten minutes faster in an hour. So, "run faster for 5 minutes" is completed
    – Tang Ho
    Commented Jun 26, 2020 at 19:58
  • I thought the sentence meant the clock is 5 minutes ahead of time, but just running at a normal speed, so then it would continue to do so. But if it means running at a faster speed, I understand it. Thank you!
    – Puco4
    Commented Jun 26, 2020 at 20:07
  • 1
    What's the difference between 这个表快了五分钟 and 这个表快五分钟? To me, there is no difference.
    – joehua
    Commented Jun 27, 2020 at 14:44
  • 2
    @joehua for me, the difference is that you wouldn't use 了 in the situation where the watch is 5 minutes faster by design.
    – Gigablah
    Commented Jun 27, 2020 at 15:55



Oh the mysteries of 了!

What is 了 doing in ‘这个表快了五分钟。’?

Not much, you can leave it out: "这个表快五分钟。" just like 芸香科橙子同学 above said.

I wouldn't even notice a difference in the mood of the sentence with or without 了。I'd get that from the tone of voice.


General discussion of the perfective or aspectual

I think I managed to understand this use of 了 in Charles N. Li, Sandra A. Thompson. Mandarin Chinese: A Functional Reference Grammar. There, they argue the perfective 了 signals an event with a perfective action, which is regarded as completely "bounded" (i.e. with an end point) either temporally, spatially or conceptually by the speaker. On the other hand, actions that are "unbounded" are referred as imperfective or durative. In English, for example in the sentence:

He was reading when his father came in.

was reading is an imperfective action (unbounded and extending in time) and came in is a perfective action (bounded and ending in time).

An event can be bounded if:

  1. Its temporal or spatial limits are specified. For example:


    He is twenty years older than me.

    二十岁 (twenty years) bounds the event.

  2. If it signals a specific event and its direct object is definite. For example:


    He spread a little butter on the bread.

    一点牛油 (a little butter) bounds the event. We note the use of 了 depends on the feeling of "boundedness" of the speaker within a context. The speaker might use 了 if he/she wants to emphasize the information in the definite direct object (considering it defines completely the event).

  3. If boundedness is inherent in the meaning of the verb sentence. For example:


    He died last year.

    死 (to die) is a bounded action with an end point.

  4. If it is followed by another event. For example:


    After I finish eating, then you eat.

    我吃完 (I finish to eat) is bounded by the subsequent event 你吃 (you eat).

A bounded action might or might not be a completed action. However, many perfective events refer to past events. Ordinarily, unless context makes clear a different time, a perfective 了 is understood to refer to past time. For more information, check the corresponding chapter of the book.

Note: The perfective or aspectual 了 should not be confused with the sentence-final or modal 了, which occurs at the end of a sentence and marks a change of state.

Our example:


This watch is running five minutes faster.

the action to be running faster is bounded temporally by five minutes, and marked as such by the speaker with the particle 了. In this case, the action does not seem to be completed (the watch might still not be readjusted).

  • I've been reading the same book as you and the section you're referencing is the only section of the book that i cant familiarize myself with. I dont understand why it is necessary to declare whether an action is bounded or not. The durative aspect in English and Mandarin both have a clear necessity whereas the perfective aspect doesn't. If you aren't using "-ing" or 在/着 then it automatically follows that you're in the perfective aspect, to mee it seems like all of the rules surrounding the use of 了 are extraneous. I understand its use as the current relevant state marker but nothing past that Commented Sep 18, 2020 at 21:28
  • Funny enough, imediately after typing that comment I had an epiphany. Is it the case that 了 in the sentence "我吃完了你吃" specifies that "你吃" must occur after "我吃完" because 了 marks the action as being closed to any further description, and the interpretation that "你吃" occurs while "我吃完" would be a contradiction of this and is therefor invalid? Commented Sep 18, 2020 at 21:34
  • @小奥利奥 I can speak of what I understood from the book. I think the perfective 了 is used to emphasize a situation is "enough bounded" from the point of view of the speaker (that is, it is a sufficient but not necessary condition to indicate the perfective aspect). From the types mentioned, types 3 and 4 might be more clearer to identify with an end point and marked with 了 (as you mentioned), while types 1 and 2 might depend more on what is specified of the situation and the context.
    – Puco4
    Commented Sep 19, 2020 at 9:43
  • In the book they say: "speakers can differ in their judgement about how much a quantified direct object serves to bound an event. For example, in the sentence 他家养了一个很可爱的小猫 'His family had a very lovable little cat', some native speakers feel that 了 is not necessary, they don't feel strongly that the quantified direct object 一个很可爱的小猫 'a very lovable little cat' renders the event bounded." Another example: "In the sentence 他问我昨天晚上做了什么?'He asked me what I did last night', out of thirty-nine speakers asked, only seven thought the 了 should be there.
    – Puco4
    Commented Sep 19, 2020 at 9:44
  • The speakers' judgement on this question depends crucially on the nature of the message they imagine the sentence is conveying. With 了, the event is viewed as bounded and thus as specific: the subject of the sentence (他 'he') was asking for a specific list of activities in which the speaker engaged (which are bounded from the context), as if 他 'he' was a nurse in charge of making sure the speaker didn't do too much. Without 了, on the other hand, the sentence is quite neutral and implies that 他 was just making casual conversation (the context does not bound the possible activities)."
    – Puco4
    Commented Sep 19, 2020 at 9:45

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