‘了’（le）is one of three vital auxiliary words in Chinese, all of which are widely used in oral or written Chinese to express grammatical features instead of using a change of word form as with English. Because of this difference, we find that foreign learners often make mistakes in knowing when and where to use ‘了’(le). Its usage is really complex, so here we will just tackle the basic usage of ‘了’.
1.‘了1’ indicates the completion and achievement of an action being used tightly behind the verb.
1) Wǒ qù kàn le nà bù diànyǐnɡ.
I have seen that movie.
2) Tā mǎi le yíbù xīn shǒujī.
He has bought a new mobile phone.
Its negative form consists of putting ‘没有’/ ‘没’ before verb and leave out ‘了’.
1) Tā méiyǒu qù ɡōnɡyuán.
He hasn’t gone to the park.
2) Mèimei méi mǎi nà tiáo qúnzi.
Younger sister hasn’t bought that skirt.
2. ‘了2’ functions as a modal particle
(a) It can be placed at the end of a sentence;
(b) It can be used to indicate that something has happened or has occurred;
(c) It can be used to show or confirm a certain fact;
(d) There usually is a time word in the sentence; if not, the sentence will indicate that something happened or occurred just now.
1) Zhōumò tā qù ɡuànɡjiē le.
He went shopping this weekend.
2) Xiàzhōusān xià le kè，wǒ bǎ shū ɡěinǐ.
Next Wednesday, I’ll give you the book.
3) Wǒ ɡānɡɡānɡ fāxiàn wǒ de diànnǎo bèi tōu le.
I discovered that my computer has been stolen just now.
4) Shànɡkè le，shànɡkè le.
Class begins, class begins.
Its negative form consists of putting ‘没有’/ ‘没’ before the verb and at the same time leave out ‘了’.
1) Shànɡkè le。→ Méi shànɡkè.
Class begins.→ Class doesn’t begin.
2) Zuótiān wǒ de zìxínɡchē huài le.→Zuótiān wǒ de zìxínɡchēméi huài.
My bike broke yesterday.→ My bike did not break yesterday.
3) Nǐ chīfàn le mɑ? Méi chī.
—Did you eat already/Have you eaten?
—Did not eat yet/Haven’t eaten yet.
3. ‘了1+2’ as a modal particle indicates a change, or in other words, something new has occurred, which is also put at the end of the sentence.
1) Xiàxuě le.
(Change of weather. It wasn’t snowy before, but now it is.)
2) Wǒ bùchī le.
I don’t want to eat.
(Change of attitude. I said I wanted to eat, but now I don’t want to eat.)
3) Wǔdiǎn le.
It’s 5 o’clock.
(Change of time)
4. Using ‘了’ at the end of a sentence and after the verb to show that something has happened and there is a completion of the action.
1) Tā qù le yīyuàn le.
He has gone to the hospital.
2) Wǒ chànɡ le yìshǒuɡē le.
I have sung a song.
Its negative form uses ‘没有’/ ‘没’ before the verb, and leaves out ‘了’. If there is a numerical word, it is usually left out also.
1) Tā méiqù yīyuàn.
He hasn’t gone to the hospital.
2) Wǒ méi chànɡɡē.
I haven’t sung.