tā wàngle dài yàoshi, zhǐhǎo zài ménkǒu děng shìyǒu lái kāimén.

She forgot to bring her keys, so she had no choice but to wait at the door for her roommate to open it.

Breakdown of tā wàngle dài yàoshi, zhǐhǎo zài ménkǒu děng shìyǒu lái kāimén.

• 她tā: she
• 在zài: at
• 了le: perfective particle

Questions & Answers about tā wàngle dài yàoshi, zhǐhǎo zài ménkǒu děng shìyǒu lái kāimén.

Why is 了 used after 忘 in 忘了带钥匙?

Here, 了 marks that the forgetting happened as a completed event in this situation.

• 忘带钥匙 can sound more general, like forget to bring keys
• 忘了带钥匙 clearly refers to this specific incident: she forgot

So 了 is attached to 忘, not to 带.

Why is it 忘了带钥匙, not 忘了带了钥匙?

Because she did not actually bring the key.

• 带钥匙 is the action she was supposed to do
• that action never happened
• so you normally do not add 了 to 带

If you said 带了钥匙, it would suggest that she did bring the key, which would contradict the meaning.

Could this also be said with 忘记 instead of 忘?

Yes. 忘 and 忘记 both mean to forget.

• 她忘了带钥匙
• 她忘记带钥匙了

Both are natural. In general:

• 忘 is a bit shorter and very common in speech
• 忘记 can sound slightly more formal or complete

In everyday Mandarin, both are used a lot.

What exactly does 带 mean here? Why not use 拿?