Hun sidder på gyngen, indtil hendes bror siger, at hun skal komme til sandkassen.

Danish very often uses position verbs where English would simply use be.

So Hun sidder på gyngen does not just mean that she is there; it also tells you her posture: she is sitting on the swing.

Common Danish position verbs are:

• sidde = sit
• stå = stand
• ligge = lie

In this sentence, sidder is the natural choice because a person on a swing is normally sitting.

Because in Danish, a swing is usually treated as something you sit on, not something you are inside.

So:

• på gyngen = on the swing
• i bilen = in the car
• i sandkassen = in the sandbox

A useful way to think about it is:

• på often goes with surfaces, seats, platforms, and things you are on
• i often goes with spaces or containers you are inside

So på gyngen is the normal wording.

That -en is the definite ending.

In Danish, instead of putting a separate word for the in front of the noun, you often add the definiteness to the end of the noun:

• en gynge = a swing

• gyngen = the swing

• en sandkasse = a sandbox
• sandkassen = the sandbox

Both gynge and sandkasse are common gender nouns, so their definite form ends in -en.

After a possessive like min, din, hans, hendes, vores, Danish normally uses the noun in its indefinite form.

So you say:

• hendes bror = her brother
• min bog = my book
• vores bil = our car

You do not normally add the definite ending as well.

So:

• broren = the brother
• hendes bror = her brother

Those are two different structures.

Because sin/sit/sine is a reflexive possessive, and it must refer back to the subject of the same clause.

Here, the clause after indtil begins with hendes bror siger. In that clause, hendes bror is the subject. Since the possessive is inside that subject phrase, sin is not the right form there. Danish uses the ordinary possessive hendes.

A very useful comparison:

• Hun vasker sin bil. = She washes her own car.
• Hun siger, at hendes bror vasker sin bil. = She says that her brother washes his own car.
• Hun siger, at hendes bror vasker hendes bil. = She says that her brother washes her car.

So sin depends very strongly on which clause you are in.

Indtil is a conjunction meaning until.

It introduces the time limit for the first part of the sentence:

• Hun sidder på gyngen = this situation continues
• indtil hendes bror siger ... = up to the point when her brother says something

So indtil marks the moment when the first situation stops or changes.

A useful contrast:

• indtil = until
• før = before

This sentence is written with start comma.

In Danish, many writers put a comma before a subordinate clause, which is why you see:

• comma before indtil
• comma before at

In modern Danish, you may also see a version without those commas, depending on the comma system being used.

So the commas here are mainly about writing style and comma rules, not about a difference in meaning.

For a learner, the important point is that indtil and at both introduce subordinate clauses.

Here at is a conjunction meaning that.

It introduces the content of what the brother says:

• hendes bror siger = her brother says
• at hun skal komme til sandkassen = that she has to come to the sandbox

English often leaves out that, but Danish very often keeps at.

Also, this is not the same at as the infinitive marker in forms like at komme. Here it is linking one clause to another.

Because skal is a modal verb, and modal verbs in Danish are followed by a bare infinitive.

So you say:

• hun skal komme
• hun vil komme
• hun kan komme

Not:

• hun skal at komme

In this sentence, skal adds the idea of obligation, instruction, or expectation: she is supposed to come.

Komme focuses on arriving at a destination or moving toward a place, often from the point of view of the person calling or waiting.

So hun skal komme til sandkassen sounds natural when someone wants her to come over there.

Gå focuses more on the way of moving, especially walking.

Compare:

• Kom herhen! = Come here!
• Gå hen til sandkassen. = Walk over to the sandbox.

So komme fits the idea of being called over to a place.

Because til marks direction or destination, while i marks location inside something.

So:

• komme til sandkassen = come to the sandbox
• være i sandkassen = be in the sandbox

In this sentence, the brother is telling her to move toward that place, so til is the natural choice.

Yes. Both indtil and at introduce subordinate clauses, and subordinate clauses follow different word-order rules from main clauses.

In this sentence, the difference is not very obvious because there is no sentence adverb like ikke. But you can see it clearly if you add one:

• Main clause: Hun skal ikke komme.
• Subordinate clause: ..., at hun ikke skal komme.

So a key rule is:

• in main clauses, the finite verb comes early
• in subordinate clauses, words like ikke usually come before the finite verb

That is one of the most important word-order patterns in Danish.

Because at hun skal komme til sandkassen is a full clause, and a full Danish clause normally needs its own subject.

So:

• hendes bror siger = one clause
• at hun skal komme til sandkassen = another clause

The second clause needs its own subject, and that subject is hun.

You cannot leave hun out here.

Because Danish often uses the present tense for future meaning when the context already makes the time clear.

That is very normal in sentences like this:

• indtil hendes bror siger = until her brother says
• hun skal komme = she has to / is supposed to come

Danish does not need a special future tense here. The time relationship is already clear from indtil and from the situation itself.

So this is completely natural Danish.