了 particle usage

Question

I've been taught that 了 particle is not used in a negative sentence, but I'm confused with this one.

“我以前很忙，但是现在不忙了。” Is this right?

I would say this. 我以前很忙，但是现在有空了。

Help please

Answer 1

了, in verb sense, means "put to the end", "terminate". You can find it in the phrase 了結 and 不了了之.

If you find it in the end of the sentence, it means something already done, for example, 知了 (acknowledged), 走了 (gone), 食了 (eaten) or changed to particular states, for example 壞了 (already turned bad), 空了 (already turned empty, emptied), 碎了 (already broken).

The same rule can applied to 不忙了, 有空了.

不忙了: (changed to) no longer busy.

有空了: (changed to) free.

For "我以前很忙，但是現在不忙了。" and "我以前很忙，但是現在有空了。", both sentence are right

Answer 2

Both “我以前很忙，但是现在不忙了。” and "我以前很忙，但是现在有空了。" are correct and of the same meaning.

"了" here is an auxilary 汉字，which can be omitted.

With "了", you express some feeling of relaxiation. Without "了", you express the contrast fact between 以前 and 现在。 However the difference is nuiance.

However, if you add "已经", for example “我以前很忙，但是现在已经不忙了。” and "我以前很忙，但是现在已经有空了。" ，then you had better keep the "了" to match "已经"

Answer 3

不……了 = not ... anymore

不忙了 = not busy anymore

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我以前学习英语，现在不学习了。I used to study English, now I don't study anymore.