Dagen efter gik hun tilbage på arbejde, fordi smerten var mindre.

Dagen efter is a fixed, natural Danish expression meaning the next day or the day after.

• dagen = the day
• efter = after

But together, dagen efter functions idiomatically as a time expression.

A native English speaker may expect a structure closer to after the day, but Danish normally uses:

• Dagen efter = the next day
• Ugen efter = the following week
• Året efter = the year after

So Efter dagen would not sound natural here.

This is because Danish follows the V2 rule in main clauses. That means the finite verb must come in the second position.

In this sentence, Dagen efter takes the first position, so the verb gik must come next:

• Dagen efter | gik | hun tilbage på arbejde

If the sentence started with the subject, then you would get:

• Hun gik tilbage på arbejde dagen efter.

Both are correct, but the word order changes because Danish main clauses require the verb in second position.

Not necessarily. Gik is the past tense of gå, which literally means walk/go, but in many contexts it simply means went.

Here, gik tilbage på arbejde means went back to work or returned to work. It does not strongly focus on the physical act of walking.

Danish often uses gå in places where English would simply use go.

Tilbage means back, and på arbejde is the usual Danish expression for at work / to work in this kind of context.

So:

• tilbage = back
• på arbejde = to work / at work
• gik tilbage på arbejde = went back to work

This is a very natural Danish way to say someone returned to work after being away.

This is a very common learner question because English often uses to work.

In Danish:

• på arbejde often refers to the state or situation of being at work, and it also appears in expressions about going back into that state.
• til arbejde is also possible in some contexts, especially when emphasizing movement toward the workplace.

But with gå tilbage or komme tilbage, Danish very naturally uses på arbejde:

• Hun gik tilbage på arbejde. = She went back to work.

Compare:

• Hun er på arbejde. = She is at work.
• Hun tog på arbejde. = She went to work.

So this is partly something you learn as a set expression.

Because fordi introduces a subordinate clause, and subordinate clauses in Danish usually have the subject before the verb.

So:

• Main clause: Dagen efter gik hun tilbage på arbejde
• Subordinate clause: fordi smerten var mindre

In the subordinate clause, the normal order is:

• subject + verb
• smerten var

This is different from the main clause, where the V2 rule applies.

Smerten is the definite form of smerte:

• en smerte = a pain
• smerten = the pain

The definite form is used because it refers to a specific pain already known from the context.

English often uses the pain in the same way, so this matches the idea of a particular pain rather than pain in general.

Mindre is the comparative form of lille or, in this context, it means less / smaller.

Here, smerten var mindre means:

• the pain was less
• the pain was less severe

You do not need end if no comparison is stated explicitly.

Compare:

• Smerten var mindre. = The pain was less.
• Smerten var mindre end i går. = The pain was less than yesterday.

So in your sentence, the comparison is understood from context.

Yes. That is also correct.

Compare:

• Dagen efter gik hun tilbage på arbejde ...
• Hun gik tilbage på arbejde dagen efter ...

The difference is mainly emphasis:

• Dagen efter ... puts the time expression first, so it feels slightly more like The next day, ...
• Hun gik ... dagen efter starts with the subject and feels a bit more neutral.

Both are natural Danish.

No. Danish does not capitalize all nouns.

Dagen is capitalized here only because it is the first word of the sentence.

So:

• dagen = lowercase in the middle of a sentence
• Dagen = uppercase at the beginning of a sentence

Unlike German, Danish does not capitalize every noun.

In modern Danish, commas before subordinate clauses can depend on which comma system is being used.

Many learners are taught that a comma is often placed before fordi, and you may indeed see:

• Dagen efter gik hun tilbage på arbejde, fordi smerten var mindre.

This is very common and fully acceptable.

In practice, comma usage in Danish can vary depending on whether someone follows traditional comma or new comma conventions. So if you see a comma before fordi, that is normal. If you are learning standard written Danish, it is a good idea to expect a comma there.

Usually, yes. Fordi most often means because and introduces a reason:

• ... fordi smerten var mindre. = ... because the pain was less.

A nearby word is for, which can also sometimes mean because in Danish, but it works differently grammatically and stylistically.

For learners, the safest choice is:

• fordi = because

That is the most straightforward and common understanding here.