Opgaven bliver rettet af læreren i morgen.

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

• opgave = assignment
• opgaven = the assignment

So the ending -n / -en often does the job that English the does.

The same thing happens with lærer → læreren:

• lærer = teacher
• læreren = the teacher

Danish often expresses definiteness with a suffix instead of a separate word.

So instead of English:

• the assignment
• the teacher

Danish uses:

• opgaven
• læreren

A separate definite word can appear in some other structures, especially with adjectives, for example den store opgave = the big assignment, but not in this simple noun form.

This is the passive voice.

• Active: Læreren retter opgaven i morgen = the teacher corrects the assignment tomorrow
• Passive: Opgaven bliver rettet af læreren i morgen = the assignment is corrected / will be corrected by the teacher tomorrow

In the passive, the focus shifts from the doer to the thing affected by the action. Here, the sentence is focusing on opgaven, not on læreren.

It is the blive-passive:

• bliver = present tense of blive
• rettet = past participle of rette

This pattern is very common in Danish:

• Bogen bliver læst = the book is being read / will be read
• Døren bliver åbnet = the door is being opened / will be opened

So bliver + past participle is one standard way to form the passive.

Because after bliver in this passive construction, Danish uses the past participle.

The verb is:

• infinitive: at rette
• present tense: retter
• past participle: rettet

So:

• retter would be a normal present-tense active form
• rettet is the form needed after bliver in the passive

That is why you get bliver rettet.

Grammatically, bliver is present tense, but because the sentence includes i morgen, the meaning is understood as future.

Danish often uses the present tense for future events when the time is clear.

So this sentence is naturally understood as something like:

• the assignment will be corrected tomorrow

This is very normal in Danish.

Yes. That is also correct.

Danish has another passive form, often called the s-passive:

• Opgaven bliver rettet
• Opgaven rettes

Both can mean roughly the same thing here.

A useful general difference is:

• blive-passive often feels a bit more like an event or process
• s-passive can sound a bit more formal, general, or written, depending on context

In many cases, both are possible, but bliver rettet is very common and easy for learners to recognize.

In a passive sentence, af introduces the agent — the person who performs the action.

So:

• af læreren = by the teacher

This is like English by in passive sentences:

• The assignment is corrected by the teacher

Do not confuse this with fra, which usually means from. In passive sentences, Danish normally uses af for the doer.

No. It can be left out if the doer is unknown, obvious, or unimportant.

For example:

• Opgaven bliver rettet i morgen = the assignment will be corrected tomorrow

That is still a complete and natural sentence. Passive sentences often omit the agent.

That is a very normal place for a time expression in Danish. Time phrases often come later in the sentence.

So this word order is completely natural:

• Opgaven bliver rettet af læreren i morgen

But Danish is flexible, and you can also move i morgen to the front for emphasis:

• I morgen bliver opgaven rettet af læreren

When you do that, the verb still has to stay in second position, so bliver comes before opgaven.

Because in Danish main clauses, the finite verb normally comes early in the sentence, usually in second position.

Here:

• Opgaven = first element
• bliver = finite verb in second position
• rettet = participle later in the verb phrase

So the structure is:

• subject + finite verb + past participle + other elements

This is a basic pattern you will see again and again in Danish.

The active version is:

• Læreren retter opgaven i morgen

That version focuses more directly on læreren as the subject.

Compare:

• Læreren retter opgaven i morgen = active
• Opgaven bliver rettet af læreren i morgen = passive

Both are correct; they just organize the information differently.

It is a natural Danish sentence. However, in everyday speech, Danish often prefers the active if the doer is known and important.

So in conversation, many speakers might more naturally say:

• Læreren retter opgaven i morgen

But the passive sentence is still perfectly normal, especially if the main topic is opgaven rather than læreren.