wǒ bǎozhèng míngtiān lái.

Mandarin word order is usually Subject + Verb + Time + Main Verb/Action here:

• 我 = subject
• 保证 = the first verb, meaning promise / guarantee
• 明天 = time expression
• 来 = the action being promised

So the sentence is structured like:

I + promise + tomorrow + come

This is natural in Chinese. Time words often come before the main action.

明天 is a time expression, and in Mandarin, time expressions usually come before the verb or action they describe.

So:

• 明天来 = come tomorrow

This is much more natural than putting 明天 after 来.

Chinese often leaves out repeated subjects when they are already clear.

So 我保证明天来 literally looks like:

I promise tomorrow come

But the subject of 来 is understood to still be 我. In fuller language, you could think of it as:

我保证，我明天来。

The second 我 is unnecessary in normal speech.

保证 means to guarantee, to assure, or to promise, depending on context.

In this sentence, it means something like I promise or I guarantee. It sounds a bit stronger and firmer than just saying you will do something.

Common uses include:

• 我保证。 = I promise.
• 我保证他会来。 = I guarantee he’ll come.
• 保证安全。 = ensure safety

So in your sentence, 保证 introduces a strong commitment.

Here, 保证 is a verb.

It can also be a noun in other contexts, but in this sentence it clearly functions as the verb:

• 我保证… = I promise / guarantee...

So the speaker is performing the act of promising.

You do not need 会 here.

Because 保证 already shows strong intention and commitment, adding 会 is optional. The sentence is already complete and natural as:

我保证明天来。

You may also hear:

我保证明天会来。

That version is also natural. Adding 会 can make the future sense a little more explicit, but it is not required.

Chinese chooses 来 or 去 based on the speaker’s point of reference.

• 来 = come toward the speaker or the relevant destination
• 去 = go away from the speaker or current reference point

So 来 is used if the person is talking about coming to where the listener/speaker expects them.

For example:

• 我明天来。 = I’ll come tomorrow.
• 我明天去。 = I’ll go tomorrow.

The correct choice depends on perspective.

Yes, sometimes.

For example, these can work:

• 我保证明天来。
• 明天我保证来。

But they are not exactly the same in emphasis.

• 我保证明天来 sounds neutral and straightforward.
• 明天我保证来 puts more focus on tomorrow, almost like Tomorrow, I promise I’ll come.

So the original sentence is very natural and unmarked.

It is natural in both speech and writing, but 保证 sounds a bit stronger and more serious than everyday casual expressions like:

• 我明天会来。 = I’ll come tomorrow.
• 我明天一定来。 = I’ll definitely come tomorrow.

Using 保证 suggests a clear promise or assurance, so it can sound more emphatic.

In speech, you might naturally make a small pause:

我保证，明天来。

But you do not have to. In normal fluent speech, people often say it smoothly as one sentence:

我保证明天来。

Both are fine.

It is pronounced bǎozhèng:

• 保 = third tone
• 证 = fourth tone

A common learner issue is making both syllables too equal. Try to keep the tones clear:

• bǎo: dipping/low third tone
• zhèng: sharp falling fourth tone

So the rhythm is roughly:

wǒ bǎozhèng míngtiān lái

Also note:

• 明天 = míngtiān
• 来 = lái

Normally, no. Without another subject, the most natural interpretation is that the speaker is the one who will come.

If you want to say someone else will come, you would usually name that person:

• 我保证他明天来。 = I guarantee he’ll come tomorrow.
• 我保证他们明天来。 = I guarantee they’ll come tomorrow.

So in 我保证明天来, the understood subject of 来 is 我.

Yes. 保证 can introduce a whole clause directly.

Examples:

• 我保证明天来。
• 我保证不迟到。 = I promise not to be late.
• 我保证完成任务。 = I guarantee I’ll finish the task.

So 保证 + clause/action is a common pattern.