了 le and liǎo

了

 le 助

1(表示动作或变化已完成)
▷ 他买了这本书。 Tā mǎile zhè běn shū. He's bought this book.

2(表示对未来的假设已完成)
▷ 下个月我考完了试回家。 Xià gè yuè wǒ kǎowánle shì huíjiā.I'll go home next month once my exams are over.

3(在句尾，表示出现变化)
▷ 下雨了。 Xiàyǔ le. It's raining.

4(在句尾，表示提醒、劝告或催促)
▷ 该回家了。 Gāi huíjiā le. It's time to go home.
▷ 别喊了！ Bié hǎn le! Stop shouting!see also lia3o

The usage of 了(le) is one of the most complex parts of Chinese grammar, partly because it has two completely different functions.

It can indicate completion of an action, e.g. 他喝了三杯啤酒(tā hēle sān bēi píjiǔ) (he drank three glasses of beer). Sometimes, when placed at the end of a clause or a sentence, it usually indicates a change of some kind, e.g. 天黑了(tiān hēi le) (it's gone dark).

了

 liǎo

I 动

1(=完毕) finish不了了之  bù liǎo liǎo zhī finish without any concrete results
▷ 了账 liǎozhàng settle a debt

2(放在动词之后表示可能)
▷ 办不了 bànbuliǎo not be able to handle
▷ 受得了 shòu de liǎo be able to bear

3(=明白) understand; to know clearly
(pt, pp understood) ▼ 明了 míngliǎo understand

II 副 (书)
▷ 了无惧色 liǎowú jùsè without a trace of fear
▷ 了无长进 liǎowú zhǎngjìn no progress at all
Please tell of the meaning of 了liǎo in the following phrases:

1. 一目了然Yīmùliǎorán obvious at a glance
2. 直截了当zhíjiéliǎodāng direct and plainspoken (idiom); blunt  / straightforward
3. 了不起liǎo bù qǐ amazing / terrific / extraordinary
4. 了不得liǎo bùdé amazing / terrific / extraordinary 
5. 了解liǎojiě to know
6. 了断liǎoduàn  to break off (a relationship etc)