Boliglånet er stort.

Because Norwegian usually writes compound nouns as a single word.

• bolig = home / dwelling
• lån = loan
• boliglån = home loan / mortgage
• boliglånet = the home loan / the mortgage

This is very common in Norwegian. Where English often uses two words, Norwegian often combines them into one.

In Norwegian, the is often built into the end of the noun.

Here:

• et boliglån = a home loan / a mortgage
• boliglånet = the home loan / the mortgage

The ending -et marks the noun as definite singular because lån is a neuter noun.

So instead of a separate word like English the, Norwegian often adds a definite ending to the noun itself.

The base form is et boliglån.

Breaking it down:

• et = the indefinite article for neuter nouns
• boliglån = home loan / mortgage

Then the definite singular form becomes:

• boliglånet = the mortgage

The main noun in the compound is lån, and that noun determines the gender of the whole compound.

Because boliglånet is a neuter singular noun, and predicative adjectives must agree with it.

The adjective stor changes like this:

• stor for common gender singular
• stort for neuter singular
• store for plural and some definite uses

Since boliglånet comes from et boliglån, it is neuter, so the correct form is:

• Boliglånet er stort.

Compare:

• Bilen er stor. = The car is big.
• Huset er stort. = The house is big.
• Bilene er store. = The cars are big.

Because after er and other similar verbs, Norwegian uses a predicative adjective, and predicative adjectives normally agree only in gender and number, not in definiteness.

So you say:

• Boliglånet er stort.
• Huset er stort.
• Bilen er stor.

Not:

• Boliglånet er det store for this meaning

That would mean something different or sound incomplete in this context.

Er means is. It is the present tense of å være, which means to be.

So:

• å være = to be
• er = is / am / are, depending on context

In this sentence:

• Boliglånet er stort. = The mortgage is large.

It can mean both, depending on context.

In this sentence, stort refers to the size/amount of the mortgage, not physical size. So it means something like:

• large
• big
• substantial

That is very natural in Norwegian.

You would normally use:

• Et boliglån er stort.

But that sentence can sound a bit general or abstract, depending on context.

A more natural generic statement might sometimes be:

• Boliglån er store. = Mortgages are large.

So the definite form boliglånet usually refers to one specific mortgage, while et boliglån refers to a mortgage in general or one unspecified mortgage.

You switch the verb and the subject:

• Er boliglånet stort? = Is the mortgage large?

This is a very common pattern in Norwegian yes/no questions:

• Han er trøtt. = He is tired.
• Er han trøtt? = Is he tired?

A rough guide for an English speaker is:

• boh-lee-glaw-neh

A few helpful points:

• å sounds like the vowel in British English law
• the stress is usually early in the word, around BO-li-glå-ne
• the final -et in stort is not a separate syllable; stort is just one syllable

Exact pronunciation varies somewhat by dialect, but that approximation is a good start.