What is the difference in use between 完 and 了?

Question

If I understood correctly, both 完 and 了 can be used to indicate a completed action, so what is the difference in use? How do we properly use 完 in a sentence? Which contexts would be valid?

Answer 1

You can use 完 and 了 together or separately.

• 了 is usually used to indicate the completion of an action. E.g. 你买了好多东西 (You purchased a lot of stuff). See the question "Tense and use of 了" to learn more.
• 完 is used to indicate the action of completing/finishing something. E.g. "說話沒完的人" (a motormouth, someone who talks to no end). Usually it's verb + 完.

完了 can have 3 different meanings/uses.

1. Verb + 完了 can indicate that the (verb) action has come to an end.
2. Noun + 完了 indicate the feeling of despair or the end of something . E.g., 哎呀，我完了！ (On no, I'm finished/done for!) or 那個車完了(That car is finished/done for!).
3. 完了 by itself (usually at the beginning of a sentence) is usually an exclamation of despair. E.g., 完了, 车没油了！回不了家了！ (We're/I'm done [for], the car's out of gas. We/I can't go [back] home [now]).

没完 can be used to describe things left undone, or something never-ending/eternal. E.g., 活儿还没完 (Work is not done/finished yet) or "說話沒完的人" (a motormouth, someone who talks to no end).

Answer 2

The other answers give some good examples, so I'll try to provide an answer from a grammatical perspective.

完 can be used as a resultative complement meaning "to finish doing something". You put it after a verb to mean that you finished doing that verb. 「吃完」 means "finish eating".

了 has many different uses, but the one that I first learned was as a past tense marker. 「吃了」 means "ate".

Now, to talk about something that you finished doing in the past, you combine the two. 「我吃完了」 means, "I finished eating."

There's a ton more detail to learn with these two words. I suggest you look at the Chinese grammar wiki complements page, the completion with 了 page, and maybe the many uses of 了 page. I expect most beginner or early intermediate textbooks will cover these topics as well.

Answer 3

I would translate 完 as "complete," and 了 as "done." 完了 would then be a very emphatic "completely done."

Answer 4

没 and 完 can be used together to indicate an action that has yet to be completed in this pattern 没 + V + 完 for example:

没看完 or 没吃完

To mean I haven't finished watching/reading it or I haven't finished eating (it)

You can also combine the two in this case it would be:

没看完了 or 没吃完了

To mean the same as above.

However the following:

没看了 or 没吃了

This means I haven't seen/read (it) or I haven't eaten (it)

e.g.

这本书我还没看了 or 他的冰淇淋还么吃了

I (still) haven't read this book or He/she hasn't eaten their ice-cream.