Hun kjøper stoffet.

Hun is the subject form of she. It is used for the person doing the action.

• Hun kjøper stoffet. = She buys/is buying the fabric/material.

Henne is the object form of her, used when something happens to her or toward her.

• Jeg ser henne. = I see her.

So in your sentence, she is the one doing the buying, so hun is correct.

In Norwegian, verbs do not change according to the subject the way they do in English.

So you get:

• jeg kjøper = I buy
• du kjøper = you buy
• hun kjøper = she buys
• vi kjøper = we buy

The infinitive is å kjøpe = to buy.
The present tense is kjøper for all persons.

That makes Norwegian easier than English in this area.

It can mean both, depending on context.

Norwegian present tense often covers both:

• she buys
• she is buying

So Hun kjøper stoffet can describe:

• a general/habitual action, or
• something happening now

If you want to make the “right now” idea clearer, Norwegian often adds a time expression or another construction, but the simple present is very common.

Because stoffet is the definite form: the fabric / the material / the substance.

Norwegian usually puts definiteness at the end of the noun as a suffix.

For a neuter noun like stoff:

• et stoff = a fabric / a material / a substance
• stoffet = the fabric / the material / the substance

So -et here is basically the Norwegian equivalent of the.

Stoff is a neuter noun in Norwegian.

That matters because neuter nouns use:

• et in the indefinite singular
• -et in the definite singular

So:

• et stoff
• stoffet

If it were a common-gender noun, the pattern would usually be:

• en in the indefinite
• -en in the definite

Not always. Stoff can mean several related things depending on context, for example:

• fabric / cloth
• material
• substance
• sometimes topic / subject matter
• in some contexts, even drugs

So even though it looks like English stuff, you should not assume it always means exactly the same thing. The context tells you which meaning is intended.

This is the normal word order for a simple main clause in Norwegian:

subject + verb + object

• Hun = subject
• kjøper = verb
• stoffet = object

So it follows a very familiar pattern for English speakers.

Also, Norwegian main clauses usually follow the verb-second rule, often called V2. In this sentence, the subject comes first, so the verb naturally comes second.

Yes, but it means something slightly different.

• stoffet = the fabric/material
• det stoffet = that fabric/material or that particular fabric/material

So det adds extra pointing or emphasis. Without det, the sentence is simply referring to the relevant fabric/material.

A rough guide:

• kj is a soft sound, somewhat like the h in some pronunciations of huge, though not exactly the same
• ø is a vowel sound that English does not really have; it is similar to the vowel in French deux or German schön
• kjøper is roughly SHUR-per or HYUR-per as a very loose approximation, but neither is perfect

The stress is on the first syllable: KJØ-per.

If you are learning Bokmål pronunciation, the exact sound can vary a bit by dialect, but the important thing is that ø should not sound like English o.

This sentence is standard Bokmål.

In Nynorsk, you would more likely see:

• Ho kjøper stoffet.

The biggest visible difference here is hun in Bokmål versus ho in Nynorsk. The rest can stay the same in this sentence.