了 suffixed to a verb
- Obligatory 了 is where it is always used with another word or structure e.g. 极 jí ‘extremely’, 太 tài ‘too’, 已经 yǐjing ‘already’.
- Specific 了 is where it is used with a specific verb object, especially if the object includes a measure word or is modified by an adjective etc. This 了 indicates that the action is complete. If the object is not modified, the sentence sounds incomplete unless 了 is added at the end of the clause. For example, 我写了信了 Wǒ xiěle xìn le 'I wrote a letter' would sound incomplete without the final 了. If the sentence contains a time measure word, e.g. 三年 sānnián, adding another 了 at the end of the sentence changes the meaning from "I did it for three years" to "I have been doing it for three years". See 了...了 Le ... le.
- If 了 is suffixed to the verb in the first clause, and the second clause starts with 就 jiù ‘then’ or 才 cái ‘only then’, the meaning is often “Having V-ed, (only) then …”.
- Future 了. Often preceded by 要 yào 'will' or 快 kuài 'soon'.
了 at the end of the clause
- Change of Situation 了 including meanings such as “get …er” and “came to …”. 了 stands at the end of the sentence in this usage.
- When Verb Suffix 了 and another 了 is used at the end of the first clause, it often indicates that it is only a clause, not a complete sentence and that something follows.
- If there is a Sequence of actions, the only 了 needed is for the last verb.
Le and Pinyin
Verb suffix le is written as part of the verb in Pinyin, unless it comes at the end of the sentence. For example:
我写了信了。 Wǒ xiěle xìn le.
It is said that 了 is the most complex part of Chinese grammar. I have tried hard in collaboration with native speakers to explain all uses of it in the below. If you disagree or have examples that disagree with these explanations, please e-mail Chris Dillon!
Specific 了, i.e. after specific objects of verbs
张先生在昨天的大会上做了一个很成功的报告。 Zhāng xiānsheng zài zuótiān de dàhuì shang zuòle yí ge hěn chénggōng de bàogào.
‘Mr Zhang gave a very successful report at yesterday's meeting.’
今天戴安娜和她的狗散了一个多小时的步，她们都非常高兴。 Jīntiān Dàiānnà hé tā de gǒu sànle yí ge duō xiǎoshí de bù, tāmen dōu fēicháng gāoxìng.
‘Diana and her dog had more than one hour’s walk today and both of them were very happy.’
Note, in the second clause, that 了 is not used with adjectives describing past states (unless there is an idea of Change of Situation).
今天大卫去了一趟图书馆，借了很多书。 Jīntiān Dàwèi qùle yítàng túshūguǎn, jièle hěn duō shū.
‘David went to the library today and borrowed many books.’
In the first case the object includes a measure word; in the second it doesn’t but is qualified by an adjective and so specific enough to need 了.
昨天是母亲节，我给妈妈买了很多鲜花，她高兴极了！ Zuótian shi mǔqinjié, wǒ gěi māma mǎile hěn duō xiānhuā, tā gāoxìng jíle!
‘Yesterday was mother's day, I bought my mother a lot of flowers, and she was thrilled!’
Note that 是 shi is not used with 了 unless there is an idea of Change of Situation. The first 了 is the Specific Object 了; the final 了 is Obligatory 了.
克利斯学了三年的汉语了，他觉得研究汉语的语法特别有意思。 Kèlìsī xuéle sán nián de Hànyǔ le, tā juéde yánjiū Hànyǔ de yǔfǎ tèbié yǒu yìsi.
‘Chris has been learning Chinese for three years now and he finds studying Mandarin grammar extremely interesting.’
The first 了 is Specific 了. The second 了 indicates that the sentence is not yet complete.
原来这里只有楼房，现在种了很多树，环境比以前好多了。 Yuánlái zhèlǐ zhǐ yǒu lóufáng, xiànzài zhòngle hěn duō shù, huánjìng bǐ yǐqián hǎo duōle.
‘There were only buildings here before, now a lot of trees have been planted, the environment is much better than before.’
The first 了 is Specific 了, the second is obligatory after 多 in this usage and also Change of Situation了.
我和她谈了十分钟，她才终于明白了我的意思。 Wǒ hé tā tánle shí fēnzhōng, tā cái zhōngyú míngbai le wǒ de yìsi.
‘I talked to her for 10 minutes; finally she understood what I meant.’
The first 了 is Specific 了; the second Specific 了.
玛丽等了大卫半个多小时了，他还没来，玛丽开始有点儿不高兴了。 Mǎlì děngle Dàwèi bàn ge xiǎoshí le, tā hái méi lái, Mǎlì kāishǐ yǒu diǎnr bù gāoxìng le.
‘Mary had been waiting for David for more than half an hour, and he still hadn’t come, so Mary started to feel a little unhappy.’
The first 了 is Specific 了, the second indicates that the sentence isn’t complete. The third 了 is Change of Situation 了.
明天就是星期六了，我还没想好这个周末做些什么。Míngtiān jiù shi xīngqīliù le, wǒ hái méi xiǎnghǎo zhège zhōumò zuò xiē shénme.
‘Tomorrow is Saturday and I don't have any idea of what I am going to do this weekend yet.’
This 了 is Future 了.
Change of Situation 了
我本来没打算去他的生日聚会，后来还是去了。Wǒ běnlái méi dǎsuàn shēngrì jùhuì, hòulái háishi qùle.
‘I had not intended to go to his birthday party at first, but somehow I went later.’
Note that 了 is not used with past negative 没 méi. The 了 is Change of Situation 了.
他今年寒假不回北京了，因为他想在伦敦过圣诞节。Tā jīnnián hánjià bù huí Běijīng le, yīnwèi tā xiǎng zài Lúndūn guò shèngdànjié.
‘He is not going back to Beijing this winter holiday, as he would like to spend his Christmas in London.’
The 了 is Change of Situation 了.
他刚刚走，你早来五分钟就见到他了。 Tā gānggang zǒu, nǐ zǎo lái wǔ fēnzhōng jiù jiàndào tā le.
‘He has just left, you would have been able to see him if you had got here only five minutes earlier.’
The first clause has no 了, as this is a sequence of actions. This sentence also works if you put another 了 after 走 zǒu.