Dataloftet er lavt.

Because Danish usually writes compound nouns as a single word.
So data + loft becomes dataloft.

This is very common in Danish, much more so than in English. English often writes similar expressions as two words, but Danish prefers one compound word.

A useful rule:

• the last part is the main noun
• it decides the word’s grammatical gender and inflection

Here, the main part is loft, so dataloft behaves grammatically like loft.

The -et is the definite article attached to the end of the noun. In Danish, the is often added as a suffix instead of being a separate word.

So:

• et dataloft = a data cap
• dataloftet = the data cap

This happens with many Danish nouns:

• et hus → huset
• et bord → bordet

Since dataloft is a neuter noun, its singular definite ending is -et.

Because dataloft is a neuter noun in Danish, so it takes et.

Danish nouns have two grammatical genders:

• common gender: usually takes en
• neuter gender: takes et

Since the final part of the compound is loft, and loft is neuter, the whole compound is neuter too:

• et loft
• et dataloft

This is a very useful pattern with compounds: the gender usually follows the last element.

Because the adjective agrees with the noun, and dataloftet is singular neuter.

With adjectives used after er in Danish, you often get:

• lav for common gender singular
• lavt for neuter singular
• lave for plural

So compare:

• Bilen er lav. = the car is low
• Huset er lavt. = the house is low
• Bygningerne er lave. = the buildings are low

Since dataloftet is neuter singular, lavt is the correct form.

Because with predicative adjectives, Danish mainly agrees for gender and number, not in the same way as when the adjective comes before a noun.

After er, you say:

• Huset er stort
• Bilen er stor
• Bilerne er store

So in Dataloftet er lavt, the adjective is predicative, and the important thing is that the subject is neuter singular. That is why it is lavt, not lave.

If the adjective came before the noun, the form would look different:

• det lave dataloft

So:

• Dataloftet er lavt = adjective after the verb
• det lave dataloft = adjective before the noun

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

So:

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

In this sentence, er simply means is:

• Dataloftet er lavt = The data cap is low

No, this is the basic Danish statement pattern:

subject + verb + complement

So here:

• Dataloftet = subject
• er = verb
• lavt = complement/adjective

This is a very normal sentence structure in Danish.

However, Danish is a V2 language, which means the finite verb usually comes second in main clauses. So if you move something else to the front, er still stays in second position:

• I dette abonnement er dataloftet lavt.

That is a broader Danish word order rule, but this sentence itself is completely straightforward.

Yes. Lav/lavt/lave can describe both physical height and a low level, amount, or limit.

So Danish uses it naturally for things like:

• a low price
• a low number
• a low limit
• a low data cap

In this sentence, lavt means the cap or allowance is low in amount, not physically low.

In the plural, both the noun and the adjective change.

Examples:

• Datalofter er lave. = Data caps are low.
• Datalofterne er lave. = The data caps are low.

Notice the pattern:

• singular neuter: lavt
• plural: lave

So lavt is only for singular neuter.

The indefinite singular would be:

• Et dataloft er lavt.

That means A data cap is low, or more naturally, A data cap is low in a general statement.

The difference is:

• et dataloft = a data cap
• dataloftet = the data cap

The adjective stays lavt in both cases because the noun is still neuter singular.

No. Danish changes the structure when an adjective comes before a definite noun.

You would say:

• det lave dataloft = the low data cap

Notice what happens:

• you add a separate definite article: det
• the adjective becomes lave
• the noun can still stay definite in this kind of structure depending on the form used, but in modern standard Danish with a preceding adjective, the normal pattern is det lave dataloft

So compare:

• Dataloftet er lavt. = The data cap is low.
• det lave dataloft = the low data cap

This is a very common difference in Danish between adjectives used after the verb and adjectives used before the noun.