Learn Hardcore Swedish: Min son borstar bara tänderna noga när han lyssnar på musik, vilket jag tycker är lite roligt. - My son only brushes his teeth carefully when he listens to music, which I think is a bit funny.

use a definite form of the noun (here: tänderna, “the teeth”),
and do not add a possessive (like mina / hans) if it’s already clear whose body it is from the subject.

So:

Min son borstar tänderna. = My son brushes (his) teeth.
You could say Min son borstar sina tänder, but it sounds less natural in everyday speech and a bit more explicit or contrastive.

If you said:

Min son borstar hans tänder.
That would normally mean My son brushes *someone else’s teeth (another male person’s).*

So tänderna alone is the normal, idiomatic choice here.

What exactly does bara mean here, and why is it placed before tänderna?

Bara means “only / just” in this sentence. Its position tells us what is being limited.

In Min son borstar bara tänderna noga när han lyssnar på musik:

The most natural reading is:
- He only brushes his teeth carefully when he’s listening to music.
- In other situations he doesn’t brush them carefully (maybe he rushes it, or doesn’t brush at all).

Could we move bara?

Min son bara borstar tänderna noga när han lyssnar på musik.
Possible, but sounds more marked. Depending on context it can sound like:
- All he does carefully when he listens to music is brush his teeth (he doesn’t do anything else carefully then).
Min son borstar tänderna bara när han lyssnar på musik.
Now bara clearly limits the time:
- He brushes his teeth only when he listens to music (and never at other times).

So the placement of bara changes what is “only”:

before tänderna/noga part: scope over the action/quality.
before när han lyssnar på musik: scope over the time/situation.

In the original sentence, bara is interpreted as limiting the careful brushing to that specific situation.

What is noga here? Is it an adjective or an adverb? Why not noggrant?

Noga here is functioning as an adverb, describing how he brushes his teeth: carefully / thoroughly.

Both noga and noggrant can be used adverbially, but:

noga is very common, everyday and neutral.
noggrant is a bit more formal or “bookish” in many contexts.

Compare:

Han läste igenom kontraktet noga.
He read through the contract carefully.
Han läste igenom kontraktet noggrant.
Same meaning, but can sound slightly more formal or emphatic.

So borstar ... tänderna noga is idiomatic, natural spoken Swedish.
Noggrant would also be correct, just a bit different in tone.

Why is it när han lyssnar på musik and not medan han lyssnar på musik? What’s the difference between när and medan?

Both när and medan can refer to time, but they are used differently:

när = when (a point in time or a period, very general).
medan = while (two things happening at the same time, often with some contrast or emphasis on simultaneity).

In this sentence:

när han lyssnar på musik = when he listens to music
Neutral, just saying at the times when he’s listening to music.
medan han lyssnar på musik = while he is listening to music
Slightly more focused on the fact that the two actions are simultaneous.

Both could work, but när is the usual, default conjunction here. Medan would add a bit more emphasis to during the period that he is listening to music, but doesn’t change the basic meaning much.

Why is it lyssnar på musik? Could we say lyssnar till musik or just lyssnar musik?

In Swedish, the normal pattern is:

lyssna på något = listen to something

So:

lyssna på musik = listen to music
lyssna på radio = listen to the radio
lyssna på henne = listen to her

Options:

lyssnar till musik
- Grammatically correct, but sounds more formal, poetic, or old-fashioned in many contexts.
lyssnar musik
- This is incorrect in standard Swedish. You need the preposition på with lyssna in this meaning.

So lyssnar på musik is the normal, everyday form.

Why is there a comma before vilket, and what does vilket refer to?

The comma and vilket together introduce a non-defining relative clause that comments on the whole situation:

..., vilket jag tycker är lite roligt.

Here:

vilket is a relative pronoun.
It is neuter singular because it refers not to a specific noun, but to the entire preceding clause:
- The fact that my son only brushes his teeth carefully when he listens to music — which I think is a bit funny.

The comma:

Marks that this is extra information / a side comment, not essential to identify anything.
In English you do something similar with a comma and which:
- ..., which I think is a bit funny.

So:

vilket = which (fact / situation) here.
The comma is required in writing before such a vilket-clause that comments on a whole clause or idea.

Why do we use vilket and not som in this sentence?

Som is the most common relative pronoun in Swedish, but:

som normally refers back to a specific noun:
- Boken som jag läser – the book that I’m reading

In this sentence, we’re not describing a noun. We’re commenting on the whole previous statement:

“that he only brushes his teeth carefully when he listens to music”

For that, Swedish usually uses vilket:

Min son borstar bara tänderna noga när han lyssnar på musik, vilket jag tycker är lite roligt.
= ..., which I think is a bit funny.

If you used som here, it would sound wrong or at least very clumsy, because som would be expected to refer to a concrete noun, and there isn’t one that fits.

Why is it tycker and not tänker or anser?

These verbs all relate to thinking or opinions, but they are used differently:

tycker
- everyday verb for having an opinion about something:
  - Jag tycker att det är roligt. = I think it’s fun / I find it fun.
tycker om
- means to like:
  - Jag tycker om musik. = I like music.
tänker
- describes the process of thinking, planning, or intending:
  - Jag tänker på dig. = I’m thinking of you.
  - Jag tänker resa imorgon. = I plan to travel tomorrow.
anser
- more formal; to consider / hold the view that:
  - Jag anser att det är fel. = I consider it wrong.

In vilket jag tycker är lite roligt, the speaker is giving a personal opinion (I find it a bit funny), so tycker is the natural choice.

Why is it är lite roligt and not är lite rolig?

Rolig/roligt is an adjective that changes form depending on what it describes:

rolig – common gender (en-word):
- En rolig film.
roligt – neuter (ett-word) or used with abstract things / whole situations:
- Ett roligt spel.
- Det är roligt. (That/it is fun.)

Here, roligt is describing the situation / fact that’s referred to by vilket (the whole previous clause). In Swedish, whole clauses and abstract “it” are usually treated as neuter, so you use roligt:

vilket jag tycker är lite roligt
= which I think is a bit funny / kind of amusing.

Lite here means “a little / a bit”. You could also say:

... vilket jag tycker är ganska roligt. – which I think is quite funny.

But lite roligt sounds milder, more modest.

Could we say Min son borstar tänderna bara när han lyssnar på musik? How does that change the meaning?

Yes, you can say:

Min son borstar tänderna bara när han lyssnar på musik.

This word order shifts the focus of bara:

Original:
- Min son borstar bara tänderna noga när han lyssnar på musik
- Most natural reading: He only brushes carefully in that situation. He might still brush (but less carefully) at other times.
New version:
- Min son borstar tänderna bara när han lyssnar på musik
- Stronger meaning: He only brushes his teeth when he listens to music; he doesn’t brush at all at other times.

So:

bara noga när = only carefully in that situation.
bara när = only at that time; not at other times.

Why don’t we say borstar sig tänderna like in some other languages?

In Swedish, you normally do not use a reflexive pronoun (sig) with verbs like “brush” when talking about a body part. Instead you:

use a normal verb, and
put the body part in the definite form, without a possessive:

Examples:

Han tvättar händerna. – He washes his hands.
Hon kamma håret. – She combs her hair.
Min son borstar tänderna. – My son brushes his teeth.

If you said borstar sig tänderna, it would sound ungrammatical in standard Swedish. The reflexive sig is used in other structures:

Han tvättar sig. – He washes himself.
Hon klär på sig. – She gets dressed.

But once you specify the body part, you usually drop sig and use the definite noun instead.

Why is it min son and not mitt son?

Swedish has two grammatical genders:

en-words (common gender)
ett-words (neuter gender)

The possessive pronouns have to match this gender:

min – for en-words (singular)
mitt – for ett-words (singular)
mina – for plural

Son is an en-word:

en son – a son
therefore: min son – my son

If the noun were neuter, you’d use mitt:

ett barn – a child → mitt barn – my child

So min son is correct; mitt son would be wrong.

Why is it just musik and not musiken in lyssnar på musik?

In Swedish, when you talk about something in general, you often use the indefinite, uncountable form with no article:

Jag gillar musik. – I like music.
Hon dricker kaffe. – She drinks coffee.

Here, lyssnar på musik means listens to music in general, not a specific piece or event.

You would use musiken (definite form, “the music”) when you mean some specific music that both speaker and listener know about:

Han lyssnar på musiken vi spelade igår.
He’s listening to the music we played yesterday.

In the original sentence, it’s about the habit whenever he’s listening to music (in general), so musik (without article) is correct and natural.