Om hon blir sjuk igen, måste arbetsgivaren boka om allt.

In Swedish, om often means if when it introduces a condition:

• Om hon blir sjuk igen ... = If she gets sick again ...

This is very common in conditional sentences.

Be careful, though: om can mean other things in other contexts. In this sentence, the first Om means if, but the later om in boka om is part of a verb and means something different.

Because bli sjuk means get sick / fall ill, while vara sjuk means be sick.

So:

• hon blir sjuk = she gets sick
• hon är sjuk = she is sick

In this sentence, the idea is that she may become ill again, not that she already is ill.

Swedish often uses the present tense in time clauses and condition clauses when English also talks about the future.

So Swedish says:

• Om hon blir sjuk igen ...

even though in English we say:

• If she gets sick again ...

This is normal Swedish usage. You do not need a special future form here.

Because Om hon blir sjuk igen is a subordinate clause, introduced by om.

In Swedish:

• main clauses usually follow the V2 rule, where the finite verb comes in the second position
• subordinate clauses do not use V2 in the same way

So in a subordinate clause, the normal order is:

• om + subject + verb
• om hon blir ...

That is why you get hon blir, not blir hon.

The comma separates the conditional clause from the main clause:

• Om hon blir sjuk igen, måste arbetsgivaren boka om allt.

This is similar to English punctuation after an introductory if clause.

In Swedish, commas in this kind of sentence are often used for clarity, especially when the subordinate clause comes first.

Because arbetsgivaren is the definite form, meaning the employer.

Swedish usually marks definiteness with a suffix attached to the noun:

• en arbetsgivare = an employer
• arbetsgivaren = the employer

So instead of using a separate word like the, Swedish often adds -en or -et to the noun.

Because Swedish usually puts the definite article at the end of the noun as a suffix.

So:

• arbetsgivare = employer
• arbetsgivaren = the employer

This is one of the basic differences between English and Swedish.

Because modal verbs in Swedish are followed directly by the infinitive, without att.

So:

• måste boka
• kan boka
• vill boka
• ska boka

Not:

• måste att boka

This works much like English:

• must book
• not must to book

Boka om means rebook, reschedule, or book again differently, depending on context.

So:

• boka = book
• boka om = rebook / reschedule

In this sentence, it means the employer has to rearrange or reschedule everything.

This is a very useful Swedish particle verb.

No. They look the same, but they do different jobs here.

• Om at the beginning = if
• om in boka om = part of the verb boka om, meaning rebook/reschedule

So they are not being used in the same way, even though the spelling is identical.

Because allt is the object of boka om:

• boka om allt = rebook everything

This is normal Swedish word order here:

• modal verb: måste
• infinitive: boka
• particle: om
• object: allt

So the final part stays together as a verb phrase meaning rebook everything.

Igen means again, and here it goes with blir sjuk:

• blir sjuk igen = gets sick again

Its placement is very natural in Swedish. It usually comes after the adjective or near the end of that part of the clause.

Compare:

• Hon är här igen. = She is here again.
• Hon blir sjuk igen. = She gets sick again.

Yes, but it changes the meaning.

• Om hon blir sjuk igen = If she gets sick again
• Om hon är sjuk igen = If she is sick again

So the first focuses on becoming ill, and the second focuses on the state of already being ill.

Both are grammatical, but they do not mean exactly the same thing.