Hon jämför sin översättning med lärarens och ser varför min var fel.

Because sin is the reflexive possessive in Swedish. It is used when the owner is the same as the subject of the clause.

Here, the subject is hon, so sin översättning means her own translation.

Compare:

• Hon jämför sin översättning = She compares her own translation
• Hon jämför hennes översättning = She compares another woman’s translation

Also, sin changes form depending on the noun:

• sin for an en-word singular
• sitt for an ett-word singular
• sina for plural

Since översättning is an en-word and singular, sin is the correct form.

Lärarens means the teacher’s.

It is formed from:

• läraren = the teacher
• lärarens = the teacher’s

Swedish usually makes the genitive by adding -s to the noun phrase.

So:

• läraren → lärarens
• Anna → Annas
• eleven → elevens

In this sentence, lärarens stands for lärarens översättning because the noun is understood from context.

Because Swedish, like English, often leaves out a repeated noun when it is obvious.

So:

• sin översättning med lärarens
  really means
• sin översättning med lärarens översättning

But repeating översättning would sound unnecessary.

This works much like English:

• her translation and the teacher’s

where translation is omitted after teacher’s because it is already clear.

Here min means my one or mine, with översättning understood.

So:

• min var fel = my translation was wrong

Swedish often uses possessive words this way when the noun is clear from context.

The form min is used because the hidden noun is översättning, which is:

• singular
• an en-word

If the hidden noun were an ett-word, you would use mitt.
If it were plural, you would use mina.

Var is the past tense of är.

So:

• är = is
• var = was

In this sentence, ser varför min var fel means she understands why the speaker’s translation was wrong.

This can suggest that she is looking at a translation that was done earlier and now sees the mistake.

In some contexts, är could also be possible if the speaker wanted to say the translation is still wrong now. But var is very natural when talking about a completed attempt or earlier version.

Because this is an embedded question, not a direct question.

After verbs like ser, vet, förstår, and undrar, Swedish uses embedded-question word order, where the subject comes before the verb.

So:

• Varför var min fel? = direct question: Why was mine wrong?
• Hon ser varför min var fel. = embedded question: She sees why mine was wrong.

That is why there is no inversion here.

Because Swedish does not need to repeat the subject when two verbs share the same subject and are joined by och.

So:

• Hon jämför ... och ser ...

means:

• She compares ... and sees ...

This is normal and works the same way in English. You could repeat hon, but it would usually sound unnecessary here.

The verb jämföra normally takes med when you compare one thing with another:

• jämföra A med B = compare A with B

So:

• Hon jämför sin översättning med lärarens
  = She compares her translation with the teacher’s

This is the standard Swedish pattern.

Here fel means wrong or incorrect, and it is used after var as a predicate word:

• min var fel = mine was wrong

This is a very common Swedish use of fel:

• Det är fel. = That is wrong.
• Svaret var fel. = The answer was wrong.

So in this sentence, fel is describing the translation as incorrect.