En mygga bet henne på armen, så nu vill hon sitta inne.

Because mygga is a common-gender noun in Swedish, and common-gender nouns take en.

• en mygga = a mosquito
• myggan = the mosquito

In Swedish, every noun is either en-gender or ett-gender, and you usually have to learn that together with the noun.

Bet is the past tense of bita, which means to bite.

This is an irregular verb:

• infinitive: bita
• present: biter
• past: bet
• supine: bitit

So En mygga bet henne means A mosquito bit her.

Because they do different jobs.

• hon = she (subject form)
• henne = her (object form)

In the sentence:

• En mygga bet henne → henne is the object, because the mosquito bit her
• nu vill hon sitta inne → hon is the subject, because she wants to sit indoors

This is similar to English she/her.

Swedish often uses the definite form of body parts where English would use a possessive.

So Swedish commonly says:

• på armen = on the arm
• i handen = in the hand
• i huvudet = in the head

When it is already clear whose body part it is, Swedish often prefers this structure instead of hennes arm.

So En mygga bet henne på armen is the natural Swedish way to say that the mosquito bit her on the arm.

Because Swedish often uses the definite form for body parts in this kind of sentence.

• arm = arm
• armen = the arm

Even though English says on the arm, Swedish is not thinking of a random arm; it is referring to a specific body part of the person already mentioned. That is why armen is used.

Here så means so or therefore.

It connects the two ideas:

• a mosquito bit her on the arm
• as a result, now she wants to sit indoors

So så shows consequence.

Be aware that så can have other meanings in Swedish too, depending on context, such as so, then, or like that.

Nu means now.

It shows that this is her current reaction after being bitten. Without nu, the sentence would still make sense, but nu makes the time frame clearer and more natural:

• så vill hon sitta inne = so she wants to sit indoors
• så nu vill hon sitta inne = so now she wants to sit indoors

This is because Swedish main clauses follow the V2 rule: the finite verb usually comes in the second position.

Here, så works as a connector, and nu is placed before the verb in the next clause. That gives:

• så nu vill hon sitta inne

The finite verb vill comes before the subject hon.

This kind of word order is very common in Swedish when something other than the subject comes first in the clause:

• Nu vill hon sitta inne
• I dag kommer han inte
• Efter jobbet ska vi hem

Sitta inne literally means sit inside/indoors, but in natural English it often means stay indoors.

Swedish often uses verbs like sitta, stå, and ligga in ways that are a bit broader than English. Here, sitta inne does not necessarily mean she is literally sitting in a chair the whole time. It can simply suggest being indoors rather than outside.

So in context, it may feel closer to:

• sit indoors
• stay inside
• stay indoors

Both can work, but they are not exactly the same.

• vara inne = be inside / be indoors
• sitta inne = sit indoors / stay indoors

Sitta inne can feel a bit more concrete or natural in everyday speech, especially when talking about choosing to remain indoors. It gives a slightly more lived-in, physical sense than the more neutral vara inne.

They are related, but they are used differently.

• inne = inside, indoors, on the inside
• in = in, into

Examples:

• Hon är inne. = She is inside.
• Hon går in. = She goes in.

So in this sentence, inne is correct because it describes location, not movement.

A very natural English rendering might be:

• A mosquito bit her on the arm, so now she wants to stay inside.

That helps show one useful point about Swedish: even when the verb is literally sit, the natural English translation may sometimes be stay depending on context.