The modal particle 了 (1)
In Chinese, 了 (le) comes at the end of a sentence, or at a slight pause inside it, and marks a change of state or a new situation.
A negative answer uses 没 (méi), and 了 is not put at the end.
What it means
……了
Meaning:
the state has changed
a new situation has come about
下雨了
下雨xiàyǔrain
了lemarks the new situation
Before it was not raining; now it is.
十二点了，吃午饭吧
十二点shí'èr diǎntwelve o'clock
了lemarks the time reaching a new point
吃午饭吧chī wǔfàn balet's have lunch
Here 了 says the time has moved on — it is now twelve.
The negative answer
If the answer is negative, 没 is used and no 了 appears at the end.
弟弟起床了吗？
没起床呢
没méinot yet
起床qǐchuángget up
呢nemarks the situation as still going on
This negative answer carries no 了.
The rule in short
When the state changes
……了
Examples:
下雨了
十二点了
The negative answer
没 + verb
No 了 at the end.
Example:
没起床呢