Hun hviler sig i sofaen, fordi hun er træt efter arbejdet.

In this sentence, hvile sig means to rest / to take a rest. It is a very common reflexive expression in Danish.

Using just hvile can sound different. Hvile on its own often means something more like lie/rest physically on something or appears in more formal/literary uses.

So:

• Hun hviler sig = She is resting
• Bogen hviler på bordet = The book rests on the table

In other words, hvile sig is the natural choice when a person is relaxing or recovering.

Sig is a reflexive pronoun. It refers back to the subject of the clause, here hun.

So Hun hviler sig literally works like She rests herself, although in natural English we just say She is resting.

Why not hende?

• sig = refers back to the subject
• hende = means her as a separate object

Compare:

• Hun hviler sig = She is resting
• Hun ser hende = She sees her

In the second sentence, hende would mean another female person, not the same person as hun.

This is a very common difference between Danish and English.

Danish often uses i with places where you sit or lie in a somewhat enclosed or contained way, including:

• i sofaen = on/in the sofa
• i sengen = in bed
• i stolen = in the chair

English usually says on the sofa, but Danish naturally says i sofaen in many cases.

You may also hear på sofaen, but i sofaen is very natural when the idea is that someone is sitting or lying comfortably in it.

Because Danish usually adds the definite article to the end of the noun instead of using a separate word like English the.

Examples:

• en sofa = a sofa

• sofaen = the sofa

• et arbejde = a job / a piece of work / work
• arbejdet = the work

The ending depends on the noun’s grammatical gender:

• en-words often take -en in the definite form
• et-words often take -et

So:

• sofa is an en-word → sofaen
• arbejde is an et-word → arbejdet

Yes. In this sentence, efter arbejdet means after work or after the workday.

The definite form arbejdet can make it sound like the work she has just finished, or the workday as a specific thing.

You may also hear efter arbejde, which is also common and can sound a bit more like the general fixed expression after work.

So both are possible, but:

• efter arbejdet = after the work / after the workday
• efter arbejde = after work

In your sentence, efter arbejdet is completely natural.

Danish main clauses normally follow the V2 rule, which means the finite verb comes in the second position.

Here the first element is Hun, so the verb hviler comes next:

• Hun
  • hviler
    • sig i sofaen

This is the normal order for a statement.

If another part of the sentence comes first, the subject moves after the verb:

• I sofaen hviler hun sig

That is also grammatical, but it gives a different emphasis.

Yes, fordi introduces a subordinate clause, and subordinate clauses in Danish have different word order from main clauses.

In your sentence:

• fordi hun er træt

This may look similar to English, but the difference becomes clearer when you add an adverb such as ikke:

• fordi hun ikke er træt = because she is not tired

Notice that ikke comes before the finite verb er in the subordinate clause.

So a useful pattern is:

• fordi + subject + adverb + verb

Your sentence has no adverb there, so the word order looks simpler:

• fordi hun er træt

No—Danish adjectives do not change for masculine vs. feminine the way some languages do.

Here, træt is a predicate adjective after er, and with a singular subject like hun, the normal form is træt.

So:

• Hun er træt = She is tired
• Han er træt = He is tired

For plural, you usually get trætte:

• De er trætte = They are tired

So hun does not trigger a special feminine adjective form.

No, Danish normally needs an explicit subject in both clauses.

So:

• Hun hviler sig i sofaen, fordi hun er træt...

The second hun is necessary because fordi hun er træt is a full clause of its own.

English also keeps the subject here: because she is tired. Danish works the same way. You generally cannot omit the subject the way some other languages can.