Døren er låst, så jeg kan ikke komme ind.

Because døren means the door, while dør means door.

In Danish, the definite article is usually attached to the end of the noun:

• en dør = a door
• døren = the door

This is very different from English, where the is a separate word.

Because dør is a common gender noun in Danish, and common gender nouns usually form the definite singular with -en.

So:

• en dør = a door
• døren = the door

Compare:

• en bil → bilen
• en stol → stolen

If a noun were neuter instead, it would usually take -et in the definite singular:

• et hus → huset

In Danish, er låst is made up of:

• er = is
• låst = locked

Here, låst is the past participle of låse (to lock), and it works like an adjective/state description.

So Døren er låst literally matches English quite closely: The door is locked.

You will often see this pattern in Danish:

• Vinduet er åbnet = The window is opened / has been opened
• Butikken er lukket = The shop is closed
• Døren er låst = The door is locked

Låst is the past participle of the verb låse (to lock).

Basic forms:

• at låse = to lock
• låser = lock/locks
• låste = locked
• låst = locked

In Døren er låst, låst describes the state of the door: it is in a locked state.

Because så here means so, and it is acting as a coordinating conjunction. After a coordinating conjunction, Danish normally keeps main clause word order.

So:

• Døren er låst, så jeg kan ikke komme ind.

This is like joining two full main clauses:

1. Døren er låst.
2. Jeg kan ikke komme ind.

After så, the subject stays before the verb:

• så jeg kan ...

This is different from adverbs like derfor (therefore), which do trigger inversion:

• Døren er låst, derfor kan jeg ikke komme ind.

So this contrast is useful:

• så jeg kan ikke ...
• derfor kan jeg ikke ...

Because in Danish main clauses, ikke usually comes after the finite verb.

Here, the finite verb is kan:

• jeg kan ikke komme ind

That is the normal order.

A helpful pattern is:

subject + finite verb + ikke + infinitive/rest

Examples:

• Jeg kan ikke svømme. = I cannot swim.
• Han vil ikke gå. = He does not want to go.
• Vi kommer ikke i dag. = We are not coming today.

So jeg kan ikke komme ind is exactly what you should expect.

Because komme ind is the natural Danish expression for come in / get in / enter in this context.

• komme = come
• ind = in

Together, they form a very common verb phrase:

• komme ind = come in / get inside

So jeg kan ikke komme ind means that the speaker cannot get inside.

This is similar to English phrasal verbs, where a small word like in, out, up, etc. is important to the meaning.

Yes, but it would mean something different or sound incomplete in this context.

• jeg kan ikke komme = I can't come
• jeg kan ikke komme ind = I can't come in / get in

Without ind, the idea of entering is missing. Since the problem is that the door is locked, komme ind is the natural choice.

Because kan is a modal verb, and after a modal verb, Danish normally uses the infinitive of the main verb.

So:

• kan = can
• komme = come

That is why you get:

• jeg kan komme
• jeg kan ikke komme ind

Not:

• jeg kan kommer ind ❌

The same happens with other modal verbs:

• jeg vil komme = I want to come
• du må gå = you may go
• han skal arbejde = he must work

Not always. Danish has several words that can match English so, depending on meaning.

In this sentence, så means therefore / as a result, and it works well.

But English so can also mean:

• very → så
  
  • so big = så stor
• in order that → often så ... at or another structure
• therefore → så, derfor

In your sentence, så is the natural everyday way to link cause and result:

• Døren er låst, så jeg kan ikke komme ind.

Yes, but the word order changes.

With så:

• Døren er låst, så jeg kan ikke komme ind.

With derfor:

• Døren er låst, derfor kan jeg ikke komme ind.

Why? Because derfor is an adverb placed in the first position of the clause, and Danish main clauses then require verb-second word order:

• derfor kan jeg ...

So both are possible, but the structure is different.

The tricky part is ø, which is a front rounded vowel that English does not really have.

A rough guide:

• dør sounds somewhat like dur or der said with rounded lips, but neither is exact.
• døren is roughly DUR-en or DER-en with rounded lips, but again only approximately.

A few points:

• ø is not like English o
• You should keep the tongue fairly forward in the mouth
• Round your lips while making the vowel

Also, the r in Danish often affects the vowel and is not pronounced as strongly as in many English accents.

Because the speaker is first stating the reason or situation:

• The door is locked

Then the consequence:

• so I can't get in

This is a natural information order in both Danish and English. Danish is flexible about what comes first, but here the locked door is the cause, so it makes sense to mention it first.

Yes.

• er is present tense of være (to be)
• kan is present tense of kunne (can / be able to)

So the whole sentence describes a present situation:

• the door is locked
• I cannot get in

Even though låst comes from a past participle, the sentence itself is describing the current state.

Usually, in a simple sentence like this, komme ind stays together at the end:

• jeg kan ikke komme ind

In some sentence types, small particles like ind may appear in slightly different positions, especially in more complex structures, but for a learner, the safest and most natural pattern is:

• subject + modal + ikke + infinitive + particle

So this sentence is a very good model to copy.

The structure is:

Døren er låst, så jeg kan ikke komme ind.

Which breaks down as:

1. Døren = subject
2. er = finite verb
3. låst = complement/state
4. så = coordinating conjunction
5. jeg = subject
6. kan = finite verb
7. ikke = negation
8. komme ind = infinitive verb phrase

So it is basically:

[statement of cause], so [statement of result]

That makes it a very useful model sentence for everyday Danish.