Det ser ut som om sjøsyken kommer tilbake.

Here, det is a dummy subject. Norwegian often uses det in sentences where English would use it in a similar vague way:

• Det ser ut som om ... = It looks as if ...
• Det virker som om ... = It seems as if ...

This det does not refer to a specific thing. It is just there because Norwegian usually wants a subject in the sentence.

Ser ut som om means something like:

• looks as if
• seems as if
• appears as though

So the sentence is built around an expression, not just the literal meanings of the individual words.

Breaking it down literally:

• ser = sees / looks
• ut = out
• som om = as if

But you should learn det ser ut som om as a set phrase meaning it looks as if / it seems that.

In this sentence, som om works together as a fixed expression meaning as if.

So:

• Det ser ut som om ... = It looks as if ...

This is very natural Norwegian. You should think of som om as one unit here.

You may also hear related patterns such as:

• Det ser ut som at ...
• Det ser ut til at ...

All of these can mean roughly it seems/looks like ..., though usage can vary a bit by style and speaker.

Yes, basically. Å se ut means to look / to appear.

Compare:

• Hun ser trøtt ut. = She looks tired.
• Det ser ut som om det regner. = It looks as if it’s raining.

So in your sentence, ser ut is not literally sees out. It is part of the expression å se ut.

Sjøsyken means the seasickness.

The base noun is:

• sjøsyke = seasickness

And sjøsyken is the definite singular form:

• sjøsyke = seasickness
• sjøsyken = the seasickness

In this sentence, Norwegian uses the definite form because it refers to a specific condition that is returning.

Because the sentence is talking about the seasickness, not seasickness in a general abstract sense.

• Sjøsyke er vanlig i uvær. = Seasickness is common in rough weather.
• Sjøsyken kommer tilbake. = The seasickness is coming back.

The ending -en is the definite ending.

Norwegian often uses the present tense where English might also use the present progressive.

So:

• kommer tilbake can mean comes back or is coming back

In context, it usually means something happening now or starting to happen again.

This is very common in Norwegian:

• Det regner. = It is raining
• Han sover. = He is sleeping
• Sjøsyken kommer tilbake. = The seasickness is coming back

Tilbake means back or back again.

So:

• komme tilbake = come back / return

Examples:

• Hun kommer tilbake i morgen. = She is coming back tomorrow.
• Smerten kom tilbake. = The pain came back.

In your sentence, kommer tilbake means that the seasickness is returning.

Sometimes yes, but not always with exactly the same nuance.

• tilbake often emphasizes returning
• igjen often emphasizes again

So:

• Sjøsyken kommer tilbake. = The seasickness is coming back / returning.
• Jeg blir sjøsyk igjen. = I’m getting seasick again.

In this sentence, tilbake sounds very natural because the idea is that something unpleasant has returned.

Yes. Som om introduces a subordinate clause.

The clause is:

• som om sjøsyken kommer tilbake

A useful thing to remember is that subordinate-clause word order shows up clearly when you add something like ikke:

• Det ser ut som om sjøsyken ikke kommer tilbake.

Notice that ikke comes before the verb kommer in the subordinate clause.

That is a classic sign of Norwegian subordinate word order.

Because after som om, you are inside a subordinate clause, and Norwegian subordinate clauses normally use regular subject + verb order.

So:

• som om sjøsyken kommer tilbake

not:

• som om kommer sjøsyken tilbake

The second version would be wrong here.

Yes. Some common alternatives are:

• Det ser ut til at sjøsyken kommer tilbake.
• Det virker som om sjøsyken kommer tilbake.

These all mean roughly the same thing:

• It looks/seems as if the seasickness is coming back.

The original sentence is natural and idiomatic.

No. In this sentence, om does not mean about.

Here it is part of som om, which means as if.

That is different from examples like:

• en bok om Norge = a book about Norway

So you should not translate this om by itself here.

A rough guide is:

• sjø sounds a bit like shur or shuh depending on accent
• syken has a long y sound, which English does not really have

A very rough English-style approximation might be:

• SHUR-sy-kehn

But that is only approximate.

A few useful pronunciation notes:

• sj in sjø is like English sh
• ø is a rounded vowel that English does not really have
• y in syken is also a rounded front vowel, not like English y

No, it is quite natural and normal. It works well in everyday speech and writing.

It sounds like something someone might say on a boat or ferry when they start feeling ill again:

• Det ser ut som om sjøsyken kommer tilbake.

So it is not especially formal, and it is not unnatural or bookish either.