Jeg hakker løg til suppen, mens min søster koger ris.

Because they are in the present tense.

In Danish, the present tense is usually formed by adding -r to the infinitive:

• at hakke → hakker
• at koge → koger

So:

• jeg hakker = I am chopping / I chop
• min søster koger = my sister is cooking / cooks

Danish present tense does not change for different subjects, so you also get:

• jeg koger
• du koger
• han/hun koger

The form stays the same.

Because Danish often uses bare nouns when talking about ingredients, food, or substances in a general sense.

So:

• hakker løg = chopping onion/onions
• koger ris = cooking rice

This is similar to English in some cases:

• I’m cooking rice
• I’m chopping onion / onions

With food words, Danish often does not need an article where English sometimes does.

In this sentence, it is most naturally understood as onions or onion as an ingredient.

That is because løg without an article can be used quite generally in cooking contexts. Danish often leaves it to context whether you mean:

• one onion
• several onions
• onion as an ingredient

So jeg hakker løg is a very natural kitchen sentence, even though English often prefers I’m chopping onions.

Because Danish usually puts the definite article at the end of the noun.

• en suppe = a soup
• suppen = the soup

So -en here is the equivalent of English the.

This happens with many common-gender nouns:

• en bil → bilen
• en søster → søsteren
• en suppe → suppen

In this sentence, suppen is definite because it refers to a specific soup that they are making.

Here, til means for.

So:

• løg til suppen = onions for the soup

This is a very common use of til in Danish: it can show purpose or what something is intended for.

Examples:

• brød til suppen = bread for the soup
• sukker til kaffen = sugar for the coffee

So this is not really about movement to the soup, but about what the onions are meant for.

Because mens introduces a subordinate clause, and subordinate clauses in Danish normally keep the order:

conjunction + subject + verb

So:

• mens = while
• min søster = subject
• koger = verb

That gives:

• mens min søster koger ris

In a main clause, Danish normally follows the verb-second rule. But after a subordinating conjunction like mens, you do not do that same inversion inside the subordinate clause.

A useful comparison:

• Jeg hakker løg, mens min søster koger ris.
• Mens min søster koger ris, hakker jeg løg.

Notice that when the subordinate clause comes first, the following main clause changes word order:

• not jeg hakker
• but hakker jeg

That is classic Danish word order.

Min søster is the most basic and neutral way to say my sister.

In Danish, possessives usually come before the noun:

• min søster
• mit hus
• mine venner

You do not use the suffixed definite article at the same time in this pattern, so:

• min søster = correct
• min søsteren = incorrect

You can also say søsteren min, and that is grammatically possible, but it often sounds a bit more emphatic, specific, or more spoken/colloquial depending on context.

So for a learner, min søster is the safest default.

It can mean both, depending on context.

The verb koge basically means to boil, but with foods like rice, potatoes, or pasta, it is often the natural Danish verb for cook by boiling.

So:

• koger ris = literally boils rice
• but in natural English, you would often say cooks rice

That is why the Danish verb and the most natural English translation are not always word-for-word identical.

The comma separates the two clauses:

• Jeg hakker løg til suppen
• mens min søster koger ris

In Danish, a clause introduced by mens is a subordinate clause, and it is very common to separate it with a comma, as in this sentence.

A small extra note: Danish comma rules have had more than one accepted system, so learners may sometimes see variation in whether a comma appears before a subordinate clause. But the sentence as written is completely normal, and using the comma here is very common.