Lagerboden er frostfri.

Because -en is the usual definite singular ending for a common-gender noun in Bokmål.

So:

• en lagerbod = a storage shed / a storeroom
• lagerboden = the storage shed / the storeroom

In Norwegian, the idea of the is often attached to the end of the noun instead of being a separate word.

No. Norwegian usually does not need a separate word for the when the noun is definite by itself.

So lagerboden already means the storage shed.

A separate determiner such as den is used in other structures, especially when an adjective comes before the noun:

• den frostfrie lagerboden = the frost-free storage shed

But in Lagerboden er frostfri, there is no missing article.

It is made of three parts:

• lager = storage
• bod = shed, booth, small storage room, cupboard-like storage space
• -en = the definite singular ending

So lagerboden is literally something like the storage-shed or the storage room.

This kind of noun compounding is extremely common in Norwegian.

Because the adjective has to agree with the noun.

Here, lagerbod is a common-gender singular noun, so the predicate adjective stays in its basic form:

• en lagerbod er frostfri

Compare:

• et rom er frostfritt = a room is frost-free
• lagerbodene er frostfrie = the storage sheds are frost-free

So the forms are:

• common gender singular: frostfri
• neuter singular: frostfritt
• plural: frostfrie

Yes. It is an adjective used predicatively, meaning it comes after er.

In the sentence:

• Lagerboden = subject
• er = verb
• frostfri = predicate adjective

This is similar to English sentences like:

• The room is cold
• The door is open

So frostfri describes the condition of the storage shed.

This is the normal Norwegian main-clause word order:

• Subject + verb + complement

So:

• Lagerboden = subject
• er = verb
• frostfri = complement

It is very straightforward and works much like English The storage shed is frost-free.

Yes, in many varieties of Bokmål, nouns like bod can also be treated as feminine.

That means you may see:

• ei lagerbod = a storage shed
• lagerboda = the storage shed

But en lagerbod and lagerboden are also correct in Bokmål and are very common.

So the sentence could also appear as:

• Lagerboda er frostfri

The sentence you were given uses the common-gender form lagerboden.

It usually refers to a small storage space, storage room, shed, or storage unit, depending on context.

So in real life it could mean things like:

• a storage shed outside
• a storage room in a building
• a separate storage compartment in an apartment building

The exact English word depends on the situation, but the grammar of the sentence stays the same.

It is a compound adjective:

• frost = frost
• fri = free

So frostfri literally means free of frost.

This pattern is common in Norwegian. Compare:

• sukkerfri = sugar-free
• feilfri = flawless / error-free
• tollfri = duty-free / toll-free, depending on context

You would usually say:

• En lagerbod er frostfri

Here the noun is indefinite:

• en lagerbod = a storage shed

Compare:

• Lagerboden er frostfri = the storage shed is frost-free
• En lagerbod er frostfri = a storage shed is frost-free

So the main difference is definite vs. indefinite form.

Because predicate adjectives in Norwegian agree with gender and number, but not with definiteness in the same way adjectives before nouns do.

After er, you get:

• en bod er frostfri
• boden er frostfri

Both use frostfri.

But when the adjective comes before a definite noun, the form changes:

• den frostfrie boden

So:

• after er: frostfri
• before a definite noun: frostfrie

That difference often confuses learners at first.

If everyone already knows which storage shed you mean, Norwegian might simply say:

• Boden er frostfri

That means The shed/storage room is frost-free.

Dropping lager- is natural when the context already makes the type of bod obvious.