Seiersbetingelsen står i regelheftet.

Because Norwegian usually writes compound nouns as a single word.

So:

• seier = victory
• betingelse = condition

Together they become seiersbetingelse = victory condition.

This is very normal in Norwegian. English often uses two words where Norwegian uses one:

• rule book → regelbok
• game board → spillebrett
• victory condition → seiersbetingelse

That -s- is a linking sound often used in Norwegian compounds.

So the word is built like this:

• seier
  • s
    • betingelse → seiersbetingelse

It does not mean possession in the same way as English 's. It is just part of how many compounds are formed. Some compounds have this linking -s-, and some do not, so it is something you gradually get used to.

The ending -en is the definite article attached to the noun. In Norwegian, the is often added to the end of the noun instead of being a separate word.

• en seiersbetingelse = a victory condition
• seiersbetingelsen = the victory condition

So Norwegian does not need a separate word for the here.

Because Norwegian usually marks definiteness with an ending on the noun.

In this sentence:

• seiersbetingelsen = the victory condition
• regelheftet = the rule booklet

This is one of the biggest structural differences from English. Instead of saying the rule booklet, Norwegian often says rule-booklet-the, in effect.

Because hefte is a neuter noun.

In Bokmål:

• common gender nouns often take -en in the definite singular
• neuter nouns often take -et in the definite singular

So:

• et regelhefte = a rule booklet
• regelheftet = the rule booklet

Compare:

• en bil → bilen
• et hus → huset

This is a very common learner question.

In Norwegian, stå can be used idiomatically for text that is written somewhere. So står here means something like:

• is written
• is stated
• appears

So Seiersbetingelsen står i regelheftet does not mean the victory condition is physically standing inside the booklet. It means the information is written there.

This use is very common:

• Det står i avisa. = It says so in the newspaper.
• Hva står det på skiltet? = What does the sign say?

Because the meaning is that the text is in the booklet, as part of its contents.

Use i when something is inside a book, booklet, document, etc.:

• Det står i boka.
• Det står i kontrakten.

Use på more often for a surface, a page, a sign, a website, or a specific visible place:

• Det står på side 4.
• Det står på skiltet.
• Det står på nettsiden.

So i regelheftet is the natural choice when you mean the rule booklet as a whole.

Yes, you could say I regelheftet står seiersbetingelsen.

Both are correct:

• Seiersbetingelsen står i regelheftet.
• I regelheftet står seiersbetingelsen.

The difference is emphasis. If you put I regelheftet first, you are highlighting the location.

This works because Norwegian main clauses follow the verb-second rule. The finite verb must come in the second position:

• Seiersbetingelsen | står | i regelheftet
• I regelheftet | står | seiersbetingelsen

You could, but it is less natural if you specifically mean that the information is written there.

• står i regelheftet = is written/stated in the rule booklet
• er i regelheftet = is in the rule booklet

The version with er sounds more general and less idiomatic for text. Native speakers usually prefer står when talking about written information.

The basic forms are:

• en seier = a victory
• en betingelse = a condition
• et hefte = a booklet / pamphlet

From those you get:

• seiersbetingelse = victory condition
• seiersbetingelsen = the victory condition
• regelhefte = rule booklet
• regelheftet = the rule booklet

It is often helpful to learn Norwegian nouns together with their article:

• en betingelse
• et hefte

That makes the definite forms easier to build later.

A rough learner-friendly version is:

• Seiersbetingelsen ≈ SAI-ers-be-TING-el-sen
• står i regelheftet ≈ stor i RAY-gel-hef-tet

A few helpful notes:

• seier sounds a bit like sigh-er, but smoother and more compressed.
• står has the Norwegian å sound, which does not match English perfectly.
• The g in regel is clearly pronounced.

If you want to sound more natural, it helps to practice the rhythm of the whole sentence, not just the individual words:

• SEI-ers-be-TING-el-sen står i RE-gel-hef-tet.