Kan du stänga dörren försiktigt, så att barnet inte vaknar?

Kan du literally means can you, but in Swedish it is very commonly used to make a polite request, just like in English.

So Kan du stänga dörren ... ? means something like Can you close the door ... ?, but functionally it often means Please close the door ...

It is softer than a direct imperative like Stäng dörren.

Because it comes after kan.

In Swedish, modal verbs such as kan (can), ska (will / shall), vill (want), and måste (must) are followed by the infinitive form of the main verb.

So:

• kan stänga = can close
• vill stänga = want to close
• måste stänga = must close

Unlike English, Swedish does not use a separate to here.

Because Swedish uses a definite ending to mean the.

• dörr = door
• dörren = the door

So instead of putting a separate word before the noun, Swedish usually adds the definite article to the end of the noun.

This is very common in Swedish:

• bok = book
• boken = the book
• hus = house
• huset = the house

Barnet means the child.

The noun barn is an ett-word in Swedish:

• ett barn = a child
• barnet = the child

So the definite ending here is -et, not -en.

This is something English speakers often need to memorize: every Swedish noun belongs to either the en group or the ett group.

Because here it is being used adverbially, meaning carefully.

The basic adjective is:

• försiktig = careful

When Swedish uses many adjectives as adverbs, it often uses the -t form:

• snabb → snabbt = quick / quickly
• försiktig → försiktigt = careful / carefully

So stänga dörren försiktigt means close the door carefully.

Så att means so that.

It introduces a clause that explains the purpose or intended result:

• Kan du stänga dörren försiktigt, så att barnet inte vaknar?

The second part explains why the door should be closed carefully: to prevent the child from waking up.

This is a very common structure in Swedish.

Because after så att, you have a subordinate clause, and Swedish usually puts inte before the finite verb in subordinate clauses.

Compare:

Main clause:

• Barnet vaknar inte. = The child does not wake up.

Subordinate clause:

• ... så att barnet inte vaknar. = ... so that the child does not wake up.

This is one of the most important word-order patterns in Swedish.

A useful rule:

• In main clauses, inte usually comes after the finite verb.
• In subordinate clauses, inte usually comes before the finite verb.

Because Swedish often uses the present tense where English also uses the present tense in clauses like so that ... doesn't wake up.

The verb is:

• vakna = to wake up
• vaknar = wakes up / is waking up

In this sentence, inte vaknar means doesn't wake up.

Swedish does not need a separate auxiliary like English does here.

Good question. Swedish distinguishes between:

• vakna = wake up, become awake
• väcka = wake someone up

So in this sentence:

• barnet inte vaknar = the child does not wake up

That is intransitive: the child wakes up by itself.

If you wanted to say so that you don't wake the child, Swedish would use väcka:

• ... så att du inte väcker barnet.

English often uses wake up both ways, but Swedish often separates the two verbs more clearly.

It is polite and natural.

Kan du ... ? is a very normal way to ask someone to do something. It is neither extremely formal nor rude.

Here is a rough scale:

• Stäng dörren. = Close the door.
  More direct.
• Kan du stänga dörren? = Can you close the door?
  Polite and common.
• Skulle du kunna stänga dörren? = Could you close the door?
  A bit softer / more polite.

So the original sentence sounds perfectly normal in everyday Swedish.

The comma is common and helpful here, especially because the sentence has a main clause followed by a purpose clause.

Swedish punctuation is sometimes a bit more flexible than English punctuation in this kind of sentence, but the comma makes the structure clearer:

• Kan du stänga dörren försiktigt, så att barnet inte vaknar?

In careful written Swedish, this punctuation is perfectly good.

In informal speech, some speakers may shorten things, but så att barnet inte vaknar is the standard and clearest form.

For a learner, så att is the safest choice when you want to say so that.

So this sentence is a good model to follow.

The main stress would usually fall on the words carrying the important meaning, especially:

• stänga
• dörren
• försiktigt
• barnet
• vaknar

Function words like kan, du, så att, and inte are usually less stressed, unless the speaker wants special emphasis.

A natural rhythm would be something like:

Kan du STÄNGA DÖRREN försiktigt, så att BARNET inte VAKNAR?

The exact intonation depends on context, but that stress pattern would sound natural.