Hun fjerner plagget med en gang hun ser sømskaden.

Hun means she and it is the subject form, because she is the one doing the action.

Compare:

• Hun fjerner plagget. = She removes the garment.
• Jeg ser henne. = I see her.

So hun is used because it is the subject of the sentence.

Fjerner is the present tense of å fjerne, which means to remove, to take away, or to get rid of.

In this sentence, hun fjerner plagget means that she removes the garment.

A learner might also wonder whether tar av could be used. Sometimes it could, depending on context, but å fjerne sounds more like deliberately removing something, while å ta av often means take off in the sense of clothing or removing something from a surface/body.

Because plagget is the definite singular form: the garment.

The noun is:

• et plagg = a garment
• plagget = the garment

Norwegian usually adds the definite article to the end of the noun instead of using a separate word like English the.

Because plagg is a neuter noun.

For many neuter nouns:

• indefinite singular: et plagg
• definite singular: plagget

That -et ending is the common definite ending for neuter nouns.

Here med en gang means as soon as or immediately when.

So:

• med en gang hun ser sømskaden = as soon as she sees the seam damage

This expression can also mean right away / immediately in other contexts, so the exact English translation depends on the sentence.

Not really. Literally, the words are:

• med = with
• en gang = one time / one occasion

But as an expression, med en gang is idiomatic. You should learn it as a set phrase meaning something like immediately or as soon as.

So it is better not to translate it word for word.

Because hun ser sømskaden is a subordinate clause after med en gang.

In Norwegian subordinate clauses, the subject normally comes before the verb:

• hun ser sømskaden

But if you begin the whole sentence with that time clause, then the main clause shows inversion:

• Med en gang hun ser sømskaden, fjerner hun plagget.

So:

• inside the subordinate clause: hun ser
• in the main clause after a fronted element: fjerner hun

Sømskaden is a compound noun:

• søm = seam / stitch
• skade = damage

Together, sømskade means seam damage or damage to the seam.

Then it becomes definite:

• en sømskade = a seam damage / seam defect
• sømskaden = the seam damage

So the sentence refers to a specific seam problem that she sees.

Because skade is a common-gender noun, not a neuter noun.

So:

• en sømskade = a seam damage
• sømskaden = the seam damage

Compare that with the neuter noun plagg:

• et plagg
• plagget

This is why the two definite endings are different.

Because Norwegian often expresses definiteness by adding an ending to the noun itself.

In this sentence:

• plagget = the garment
• sømskaden = the seam damage

So English uses a separate word (the), but Norwegian usually puts that meaning at the end of the noun.

Both are in the present tense.

• fjerner = removes
• ser = sees

Norwegian often uses the present tense in sentences describing a general action, a routine, or something presented as happening at that moment.

So this sentence could mean:

• a habitual action: whenever she sees the seam damage, she removes the garment
• a present-time narration: she removes it as soon as she sees it

The broader context tells you which is meant.

Yes, often you could use så snart in a similar way:

• Hun fjerner plagget så snart hun ser sømskaden.

That also means She removes the garment as soon as she sees the seam damage.

Straks can sometimes work too, but the phrasing may shift slightly depending on style and context. Med en gang is very common and natural.

By itself, it could be either.

It can describe:

• a specific event: she removes the garment as soon as she notices the damage
• a general procedure or habit: whenever she sees seam damage, she removes the garment

Norwegian present tense often allows both readings, just like English sometimes does. Context decides.