Min termokop holder kaffen varm længere end en almindelig kop.

Because termokop is an en-word in Danish, also called a common gender noun.

Possessives change like this:

• min for en-words
• mit for et-words
• mine for plural

So:

• en termokop → min termokop
• et glas → mit glas
• kopper → mine kopper

Danish usually writes compound nouns as a single word.

So termo + kop becomes termokop.

This is very common in Danish:

• kaffekop = coffee cup
• vinterjakke = winter jacket
• soveværelse = bedroom

English often uses two words where Danish prefers one compound word.

Here holder means keeps, not just holds in the physical sense.

A very common Danish pattern is:

holde + object + adjective

meaning:

keep + object + adjective

For example:

• holde døren åben = keep the door open
• holde maden kold = keep the food cold
• holde kaffen varm = keep the coffee warm

So in this sentence, holder is part of the expression holder kaffen varm.

Kaffen is the definite form, meaning the coffee.

In this sentence, it refers to a specific coffee: the coffee in the thermos cup, or the coffee being talked about.

So:

• kaffe = coffee in a general sense
• kaffen = the coffee, a specific amount or instance of coffee

You could say holder kaffe varm in a more general or slogan-like way, but holder kaffen varm sounds more like a normal sentence about a specific situation.

Because varm is not describing the noun directly here. It is describing the state that the coffee is kept in.

Compare these:

• varm kaffe = warm coffee
• holder kaffen varm = keeps the coffee warm

In varm kaffe, varm is just an adjective before the noun.

In holder kaffen varm, the structure is keep the coffee warm, where varm comes after the object and describes the result or state.

Because varm agrees with kaffen, and kaffe is a common gender noun.

In predicative use, Danish adjectives often agree like this:

• common gender singular: varm
• neuter singular: varmt
• plural: varme

So:

• kaffen er varm
• vandet er varmt
• drikkene er varme

Since the sentence is about kaffen, the correct form is varm.

Here længere means longer in the sense of for a longer time.

It is being used adverbially, modifying how long the coffee stays warm.

So:

• længe = for a long time
• længere = for a longer time

In this sentence:

holder kaffen varm længere = keeps the coffee warm longer

End means than after a comparative.

So:

• længere end = longer than
• større end = bigger than
• bedre end = better than

This is the normal word used after comparatives in Danish.

Yes, but only in the sense that Danish, like English, often leaves out repeated words when they are obvious.

The full idea is:

Min termokop holder kaffen varm længere end en almindelig kop gør.

or

... længere end en almindelig kop holder kaffen varm.

But that would sound heavier and more repetitive. So Danish normally shortens it to:

... længere end en almindelig kop

English does the same:

My thermos cup keeps the coffee warm longer than an ordinary cup.

The verb does is understood.

Because after en + singular common gender noun, the adjective stays in its basic form.

So:

• en almindelig kop
• et almindeligt glas
• almindelige kopper

The forms are:

• common singular indefinite: almindelig
• neuter singular indefinite: almindeligt
• plural or definite: almindelige

Since kop is a singular common gender noun, almindelig is correct.

The sentence is built like this:

• Min termokop = subject
• holder = finite verb
• kaffen = object
• varm = object complement
• længere end en almindelig kop = adverbial comparison

So the structure is:

Subject + verb + object + complement + comparison

Also, Danish main clauses usually follow the verb-second rule, meaning the finite verb comes in the second position of the clause. Here the subject comes first, so the verb holder comes second.

Because it describes a general fact or a regular property of the thermos cup.

Danish often uses the present tense for:

• general truths
• habits
• product descriptions
• things that are usually true

So holder here means something like keeps or is able to keep as a normal characteristic of the cup.