nǐ jīntiān dài yàoshi le ma?

Here 带 means to bring, to carry, or to have something with you.

So 你今天带钥匙了吗？ is asking whether the person brought / has their keys with them today.

A useful comparison:

• 带 = bring along / carry with you
• 拿 = take in the hand / pick up / fetch

In this sentence, 带 is the natural choice because the focus is on whether the person came with the keys.

In Mandarin, time words often come after the subject and before the verb.

So this pattern is very common:

• 你 今天 带 钥匙 了吗？
• 我 明天 去 北京。
• 他 昨天 没来。

You can think of the order as:

subject + time + verb + object

This is one of the most common word orders in Chinese.

Here 了 marks that the action is viewed as completed or relevant up to now.

So 带了 means something like:

• brought
• did bring
• have brought

But it is important not to think of 了 as simply an English past tense marker. Chinese does not work the same way as English tense. Here, 了 is showing aspect: whether the action has happened.

In this sentence, 带了 asks whether the action of bringing the keys has happened by now.

They do different jobs:

• 了 shows the action is being treated as completed / realized
• 吗 turns the sentence into a yes-no question

So:

• 你今天带钥匙了。 = You brought/have your keys today.
• 你今天带钥匙了吗？ = Did you bring/have your keys today?

This combination, 了吗, is very common when asking whether something has happened.

Not exactly in the English grammar sense.

Chinese usually does not mark tense the way English does. Instead, it often marks whether an action is:

• completed
• ongoing
• experienced
• expected, etc.

So 你今天带钥匙了吗？ is asking whether, by now / for today, the action of bringing the keys has happened.

Depending on context, English translations could be:

• Did you bring your keys today?
• Have you brought your keys today?
• Do you have your keys with you today?

Yes. In context, 钥匙 often naturally means your key(s) even without 你的.

Chinese frequently leaves out possessives when they are obvious from context. If someone asks you this question, everyone understands they mean the keys you are supposed to have.

So:

• 你今天带钥匙了吗？ = Did you bring your keys today?
• 你今天带你的钥匙了吗？ = Did you bring your keys today?

The second version is possible, but it sounds more explicit and may be used if the speaker wants emphasis or contrast.

Chinese nouns usually do not have to show singular vs. plural the way English nouns do.

So 钥匙 can mean:

• key
• keys

The exact meaning depends on context.

In real life, if someone says 带钥匙了吗, they often mean Did you bring your key / keys? The listener understands from the situation.

Very natural answers include:

• 带了。 = Yes, I brought them / Yes, I have them.
• 带了钥匙。 = Yes, I brought the keys.
• 没带。 = No, I didn’t bring them.
• 没带钥匙。 = No, I didn’t bring the keys.
• 忘了带。 = I forgot to bring them.

Notice that in negative answers, 没 is used, not 不, because this is about whether the action happened.

Because 没 is commonly used to negate completed actions or things that did not happen.

Since the question uses 带了 and asks whether the action happened, the matching negative is:

• 没带 = did not bring

Compare:

• 我没带钥匙。 = I didn’t bring my keys.
• 我不带钥匙。 = I don’t bring keys / I’m not bringing keys

不带 sounds more like a general habit, refusal, or future intention, not a simple statement that the action failed to happen this time.

You can, but it changes the feel.

• 你今天带钥匙了吗？ asks whether the action has already happened or whether the person has the keys with them now.
• 你今天带钥匙吗？ sounds more like Will you bring keys today? or Do you bring keys today?, depending on context.

For the common meaning Did you bring your keys today?, the version with 了 is more natural.

This is a yes-no question made with 吗.

The basic statement is:

• 你今天带钥匙了。

Add 吗 to turn it into a question:

• 你今天带钥匙了吗？

This is one of the simplest and most common ways to ask yes-no questions in Mandarin.

Yes. A very natural alternative is:

• 你今天带没带钥匙？

This literally repeats the verb in a positive + negative pattern and means the same thing:

• Did you bring your keys today?

Both are common:

• 你今天带钥匙了吗？
• 你今天带没带钥匙？

The 吗 version may feel a little more straightforward for learners, while the A-not-A pattern is also very common in everyday speech.

It is pronounced yàoshi.

The first syllable is clearly fourth tone:

• yào

The second syllable, shi, is often pronounced in the neutral tone in everyday speech:

• yàoshi

That is why learners often hear it as lighter and shorter than a full tone syllable.

So when saying the full sentence naturally:

• 你今天带钥匙了吗？
• nǐ jīntiān dài yàoshi le ma?

Both 了 and 吗 are also usually in the neutral tone here.

Sometimes, but the meaning may shift slightly.

Common possibilities:

• 带 = bring along / have with you
• 拿 = take / hold / fetch
• 带上 = bring along, with a stronger sense of taking something with you

For example:

• 你今天带钥匙了吗？ = Did you bring your keys today?
• 你今天拿钥匙了吗？ = Did you take the keys?
  This may sound less natural unless the situation specifically focuses on taking them from somewhere.
• 你今天带上钥匙了吗？ = Did you remember to bring your keys along today?

So 带 is the most natural everyday choice in this sentence.

Depending on context, good translations include:

• Did you bring your keys today?
• Do you have your keys with you today?
• Have you brought your keys today?

In everyday English, Do you have your keys with you? may be the most natural in some situations, even though the Chinese literally uses bring/carry.

That is because the Chinese sentence is often really checking the present result: whether the person has the keys now.