Jag svär att jag kommer imorgon.

Because Swedish very often uses the present tense to talk about the future when the context already makes the time clear.

In Jag svär att jag kommer imorgon, kommer is the present tense of komma (to come), but with imorgon it clearly refers to the future.

This is very natural in Swedish. It works a lot like English in sentences such as I’m coming tomorrow.

It is the main verb.

Here, kommer means come / am coming, not will as a separate future helper verb.

So the structure is:

• jag = subject
• kommer = present tense of komma
• imorgon = time expression

A learner might expect something like will come, but Swedish does not need a separate future auxiliary here.

Att here means that and introduces a subordinate clause:

• Jag svär = I swear
• att jag kommer imorgon = that I’m coming tomorrow

So att connects the two parts of the sentence.

In English, that can often be left out: I swear I’m coming tomorrow.
In Swedish, att is often used in this kind of sentence, though in informal speech it can sometimes be omitted.

Yes, sometimes, especially in casual speech:

• Jag svär jag kommer imorgon.

But Jag svär att jag kommer imorgon is clearer and more standard. For learners, it is safest to keep att.

Because the second part is a new clause, and Swedish normally needs its own subject there.

So:

• Jag svär = I swear
• att jag kommer imorgon = that I’m coming tomorrow

Even though English also repeats I, learners sometimes wonder whether Swedish can skip it. In this sentence, it cannot. The second clause needs jag.

Yes, you could, but it is not exactly the same in tone.

• Jag kommer imorgon = I’m coming tomorrow / I will come tomorrow
  
  • often sounds like a plan or a firm statement
• Jag ska komma imorgon = I will come tomorrow / I’m going to come tomorrow
  
  • can sound more like intention, promise, or future plan

In your full sentence:

• Jag svär att jag kommer imorgon sounds very natural.
• Jag svär att jag ska komma imorgon is also possible, but slightly different in nuance.

Svär is the present tense of svära, which can mean to swear.

In this sentence, it means to swear / to promise very strongly / to insist very strongly.

So Jag svär att ... is a strong expression. It is not just neutral information; it adds emphasis, like:

• I swear that ...
• I really promise that ...

Be aware that svära can also mean to swear in the sense of using bad language, but that is not the meaning here.

It sounds emphatic and a bit emotional. It suggests the speaker really wants to be believed.

Depending on context, it can sound:

• serious
• persuasive
• defensive
• informal and emotional

In everyday conversation, people may use it quite casually, but it is still stronger than simply saying:

• Jag kommer imorgon.

So the sentence is not just future information; it is also a strong reassurance.

Yes. Both imorgon and i morgon are used.

• imorgon = very common modern spelling
• i morgon = also accepted

They mean the same thing: tomorrow.

Many learners will see both forms, so it is good to recognize them as equivalents.

Yes. Swedish follows V2 word order in main clauses, which means the finite verb usually comes in the second position.

So:

• Jag svär att jag kommer imorgon.

If you move imorgon to the front of the subordinate clause, you get:

• Jag svär att imorgon kommer jag.

But that version sounds unusual here.

In a simple main clause, the change is easier to see:

• Jag kommer imorgon.
• Imorgon kommer jag.

Notice that kommer stays in second position.

It actually does keep the normal subordinate-clause pattern, but this sentence is simple enough that it looks similar to English.

The clause is:

• att jag kommer imorgon

That is standard subordinate-clause order in Swedish.

A place where learners notice subordinate-clause word order more clearly is with adverbs like inte:

• main clause: Jag kommer inte imorgon.
• subordinate clause: Jag svär att jag inte kommer imorgon.

So after att, adverbs such as inte usually come before the verb in Swedish subordinate clauses.

A rough guide is svair or svehr, but the vowel ä does not match English perfectly.

A few tips:

• sv at the start is pronounced together, roughly like sv
• ä is a front vowel, somewhat like the e in bed, but not exactly
• r is pronounced in a Swedish way, which varies by region

So svär is approximately:

• svär → something like svehr

The best way to learn it is by listening to native audio, because the Swedish ä is hard to capture exactly in English spelling.

The grammar itself is completely normal, but the expression Jag svär att ... feels more spoken and emotionally marked than formal.

So:

• Jag kommer imorgon. = neutral
• Jag svär att jag kommer imorgon. = stronger, more conversational, more emotional

It is perfectly acceptable Swedish, but in very formal writing you would usually choose a less dramatic phrasing unless you specifically want that strong effect.