wǎnshang shuìjiào qián, nǐ zuìhǎo kàn yíxià mén yǒuméiyǒu suǒ hǎo.

Chinese often puts time expressions near the beginning of a sentence.

So 晚上睡觉前 sets the time frame first:

• 晚上 = at night / in the evening
• 睡觉前 = before going to sleep

Together, it means before going to sleep at night.

This is very natural in Mandarin:

• 时间 + 主语 + 其他内容
• 晚上睡觉前，你最好……
• Before going to sleep at night, you’d better...

睡觉前 means before sleeping or before going to bed.

It is made of:

• 睡觉 = to sleep / go to bed
• 前 = before

In Chinese, 前 can come after a verb phrase to mean before doing that action.

Examples:

• 吃饭前 = before eating
• 上课前 = before class / before class starts
• 睡觉前 = before sleeping

So this is a very common pattern:

• Verb + 前 = before doing something

The comma separates the opening time phrase from the main part of the sentence.

So the sentence is divided like this:

• 晚上睡觉前， = before going to sleep at night,
• 你最好看一下门有没有锁好。 = you’d better check whether the door is locked properly.

In writing, this comma makes the sentence easier to read. In speech, there would usually just be a slight pause.

最好 literally means best, but in sentences like this it often means:

• it would be best to...
• you’d better...
• it’s best if...

So 你最好看一下... means you’d better check...

It gives advice, but it is usually less blunt than a direct command.

Compare:

• 你最好看一下。 = You’d better take a look.
• 你看一下。 = Take a look.
• 你一定要看。 = You must look/check.

一下 often makes an action sound:

• brief
• light
• casual
• less harsh

So:

• 看 = look / check
• 看一下 = take a quick look / check briefly

In this sentence, 看一下门有没有锁好 means check whether the door is locked properly.

Using 一下 makes the advice sound more natural and polite. Without it, 看 is still grammatical, but a little more direct.

Here, 看 is closer to check.

Chinese 看 has a wide range of meanings depending on context:

• look
• watch
• read
• see
• check

In 看一下门有没有锁好, it does not mean just physically looking at the door. It means check and make sure whether the door has been locked properly.

Here 有没有 means whether or not there is / whether or not it has been.

In this sentence:

• 门有没有锁好 means
• whether the door has been locked properly

This is a very common way in Mandarin to express whether or not.

Pattern:

• 有没有 + verb/result
• whether or not something happened / is the case

Examples:

• 看他有没有来 = see whether he came
• 问一下有没有位子 = ask whether there are seats
• 检查门有没有锁好 = check whether the door is locked properly

Because 门 is the thing being checked, and 有没有锁好 describes its condition.

So the structure is:

• 看一下
• 门
• 有没有锁好

Literally: check the door, whether it has been locked properly

This is a very natural Chinese pattern:

• 看/检查 + object + 有没有 + verb/result

Examples:

• 看看作业有没有写完 = check whether the homework has been finished
• 看看饭有没有做好 = check whether the meal is ready
• 看看门有没有锁好 = check whether the door is locked properly

In 锁好, 好 is a result complement.

So:

• 锁 = to lock
• 锁好 = to lock properly / to have locked securely / to lock and complete the action successfully

Here 好 does not simply mean good. It often shows that:

• the action is completed
• the result is satisfactory
• the thing is properly done

Other common examples:

• 写好 = write and finish it properly
• 准备好 = get ready / prepare properly
• 关好 = close properly
• 放好 = put away properly

So 门有没有锁好 means not just whether the door was locked, but whether it was locked properly/securely.

Here, 锁 is a verb meaning to lock.

Chinese words can often function as different parts of speech depending on context.

For example:

• 锁 = lock (noun)
• 锁门 = lock the door (verb + object)
• 门锁 = door lock (noun phrase)

In 门有没有锁好, 锁 is clearly verbal:

• to lock the door properly

Chinese often leaves out the subject when it is obvious, unknown, or unimportant.

Here, the important thing is not who locked the door. The important thing is whether the door is properly locked.

So 门有没有锁好 focuses on the result/state, not the person doing the action.

In natural English, we also often do something similar:

• Check whether the door is locked.

We do not need to say:

• Check whether someone has locked the door.

Yes, 门锁好了没有 is also possible, and it means almost the same thing: has the door been locked properly or not?

But there is a slight difference in feel:

• 门有没有锁好 = a very common, smooth way to say whether the door is locked properly
• 门锁好了没有 = more directly an A-not-A style question: locked properly or not?

Both are understandable and natural. In this sentence, 门有没有锁好 sounds very standard after 看一下.

You could, but the meaning changes slightly.

• 门有没有锁 = whether the door is locked
• 门有没有锁好 = whether the door is locked properly / securely

Adding 好 makes the meaning a little more complete and practical. It suggests:

• not just that someone locked it,
• but that it was done correctly and securely.

For something like a door, 锁好 is very natural because it emphasizes the successful result.

This is because of tone change with 一.

Normally:

• 一 is first tone: yī

But before a fourth-tone syllable, it changes to second tone:

• 一下
• yí + xià

Since 下 is fourth tone, 一 becomes yí.

So:

• 一下 = yíxià

This is a regular pronunciation rule in Mandarin.

The sentence can be broken down like this:

• 晚上睡觉前， = before going to sleep at night
• 你 = you
• 最好 = had better
• 看一下 = check briefly / take a look
• 门有没有锁好 = whether the door is locked properly

So the overall pattern is:

• Time phrase + subject + advice word + verb + object clause

More abstractly:

• 什么时候，谁最好做什么，检查某件事是否完成

This word order is very typical in Mandarin:

1. set the time
2. mention the person
3. give the attitude/advice
4. say the action
5. add what is being checked or asked about