Ankomsthallen er stor.

Because Danish, like English, often forms compound nouns by joining words together.
Here, ankomst + hallen gives ankomsthallen.

A useful way to think about it is:

• ankomst = arrival
• hal = hall
• ankomsthal = arrival hall
• ankomsthallen = the arrival hall

This is very common in Danish. English sometimes writes similar ideas as two words, but Danish usually prefers one compound word.

The ending -en is the definite article attached to the noun. It means the.

So:

• en ankomsthal = an arrival hall
• ankomsthallen = the arrival hall

This is different from English, where the is a separate word. In Danish, the definite article is often added to the end of the noun.

Because Danish usually expresses the by adding an ending to the noun instead of putting a separate word in front.

Compare:

• en hal = a hall
• hallen = the hall

So in ankomsthallen, the idea of the is already built into the word. You do not need an extra article before it.

Er is the present tense of at være = to be.

So:

• jeg er = I am
• du er = you are
• den er = it is

In this sentence, er links the subject ankomsthallen with the description stor. It works just like English is in a sentence like The arrival hall is big.

This is a very common learner question.

Here, stor is a predicative adjective, meaning it comes after er and describes the subject:

• Ankomsthallen er stor.

In Danish, predicative adjectives are usually:

• common gender singular: stor
• neuter singular: stort
• plural: store

Since ankomsthal is a common gender singular noun, the adjective stays stor.

Examples:

• Hallen er stor. = The hall is big.
• Huset er stort. = The house is big.
• Hallerne er store. = The halls are big.

Because this adjective is not placed before the noun. It comes after er.

That distinction matters in Danish:

Before the noun (attributive adjective)

• den store hal = the big hall

Here, the adjective is usually store with a definite noun phrase.

After er (predicative adjective)

• hallen er stor = the hall is big

Here, the adjective agrees mainly with gender and number, not with definiteness in the same way. So stor is correct.

This is one of the most important adjective patterns in Danish.

It is a common gender noun.

You can tell because the indefinite form would be:

• en ankomsthal

In Danish, nouns are mainly:

• common gender: takes en
• neuter: takes et

Since ankomsthal is common gender, the predicative adjective is stor, not stort.

The structure is:

• Ankomsthallen = subject
• er = verb
• stor = adjective / subject complement

So the pattern is:

subject + verb + description

This is the normal word order for a simple statement in Danish, just as in English:

• The arrival hall is big.

You would usually put the verb first:

• Er ankomsthallen stor?

This is the standard yes/no question pattern in Danish:

verb + subject + rest

Compare:

• Ankomsthallen er stor. = The arrival hall is big.
• Er ankomsthallen stor? = Is the arrival hall big?

A simple learner-friendly approximation is:

AHN-komst-hal-en

A few pronunciation notes:

• ankomst has the main stress at the beginning.
• hal sounds somewhat like English hall, but with a Danish vowel quality.
• The final -en is a short unstressed ending, roughly like -en in open, but not exactly.

If you are a beginner, the most important thing is to keep the word flowing as one compound and not pause between the parts.

No. Danish does not capitalize all nouns.

In this sentence, Ankomsthallen is capitalized only because it is the first word of the sentence, not because it is a noun.

So in the middle of a sentence, it would normally be written with a lowercase letter:

• Jeg kan se ankomsthallen.

No, that would be incorrect.

In Danish, stor is an adjective, and after er you can simply use the adjective by itself:

• Ankomsthallen er stor.

If you use en, you need a noun after it:

• Ankomsthallen er en stor bygning. = The arrival hall is a big building.

So:

• er stor = correct
• er en stor = incomplete / incorrect unless a noun follows

It would be:

• En ankomsthal er stor.

Grammatically, that means An arrival hall is big or A arrival hall is big in structure, though in natural English you would usually need context.

The important forms are:

• en ankomsthal = an arrival hall
• ankomsthallen = the arrival hall

So the sentence you were given uses the definite singular form of the noun.