Læreren lærer os dansk i klassen.

Because the two forms are related but do different jobs:

• læreren = the teacher
• lærer = teaches / is teaching

So the first one is a noun, and the second one is a verb.

This is very common in Danish. The noun en lærer means a teacher, and the verb at lære means to learn or, in some contexts, to teach.

So:

• en lærer = a teacher
• læreren = the teacher
• lærer = learns / teaches

You understand which is which from the sentence structure.

The -en is the definite article attached to the end of the noun. It means the.

So:

• en lærer = a teacher
• læreren = the teacher

This is one of the big differences from English. In Danish, the is often added to the end of the noun instead of standing as a separate word.

A few more examples:

• en bog = a book
• bogen = the book
• en elev = a student
• eleven = the student

Because os is the object form of we.

Compare English:

• we teach = subject
• the teacher teaches us = object

Danish works the same way:

• vi = we
• os = us

In this sentence, the teacher is doing the action, and os receives it, so os is correct.

Because Danish does not need a separate word like English to in this pattern.

In English, we say:

• teach someone something

and not usually teach something to someone in this exact structure.

Danish uses a similar pattern:

• lære nogen noget = teach someone something

So:

• lærer = teaches
• os = us
• dansk = Danish

Together: teaches us Danish

There is no missing word here.

Yes, it can, depending on the structure.

This is something English speakers often notice quickly.

• Jeg lærer dansk. = I am learning Danish.
• Læreren lærer os dansk. = The teacher teaches us Danish.

So how do you know which meaning is intended? Usually by the pattern:

• lære + thing often means learn
• lære + someone + thing often means teach someone something

In modern Danish, undervise is also a very common verb for teach, especially in more formal or school-related contexts:

• Læreren underviser os i dansk.

But your sentence with lærer is grammatical and understandable.

Because in Danish, names of languages and nationalities are normally not capitalized.

So:

• dansk = Danish
• engelsk = English
• tysk = German

This is different from English, where we write Danish, English, German with capitals.

So dansk is correct here.

It can mean different things depending on context, but here it clearly means the Danish language.

For example:

• Jeg taler dansk. = I speak Danish.
• dansk kultur = Danish culture
• en dansker = a Dane

In Læreren lærer os dansk, the verb and sentence structure make it clear that dansk means the subject being taught: Danish.

It means in the classroom or in class, depending on context.

• i = in
• klassen = the class / the classroom

So i klassen tells you where the action happens.

Depending on situation, English might translate it as:

• in the classroom
• in class

Both can fit.

Because klassen is the definite form: the class or the classroom.

Compare:

• en klasse = a class
• klassen = the class

So:

• i en klasse = in a class
• i klassen = in the class / in class

Again, Danish often adds the definite article to the end of the noun.

This sentence uses normal Danish main clause word order:

• Læreren = subject
• lærer = verb
• os = indirect object
• dansk = direct object
• i klassen = place

So the order is very natural and straightforward.

A useful thing to know is that Danish is a verb-second language in main clauses. That means the finite verb normally comes in the second position.

For example:

• Læreren lærer os dansk i klassen.
• I klassen lærer læreren os dansk.

Both are possible, but the second one puts more emphasis on i klassen.

In this sentence:

• os = the people receiving the teaching
• dansk = the thing being taught

So you can think of it as:

• os = indirect object
• dansk = direct object

This is similar to English:

• The teacher teaches us Danish.

Here, us is the recipient, and Danish is what is taught.

It is present tense.

The infinitive is:

• at lære = to learn / to teach

The present tense is:

• lærer = learn(s) / teach(es)

So the sentence means something like:

• The teacher teaches us Danish in class or
• The teacher is teaching us Danish in class

Danish often uses the simple present where English might use either simple present or present continuous, depending on context.

The past tense of lære is lærte.

So:

• Læreren lærte os dansk i klassen. = The teacher taught us Danish in class.

A few related forms:

• at lære = to learn / teach
• lærer = learns / teaches
• lærte = learned / taught
• har lært = has learned / has taught

The letter æ is a Danish vowel that does not match a single English sound exactly, but it is somewhat like the vowel in cat, though not identical.

Very roughly:

• læ- sounds a bit like leh or lae
• reren has a soft Danish rhythm that may be hard for beginners

A very rough learner-friendly approximation is:

• LÆR-er-en
• LÆR-er

But native pronunciation is smoother than English spelling suggests.

The important beginner point is:

• æ is its own letter
• it is common in Danish
• you should not pronounce it like English ay

Yes, that is also a good Danish sentence.

There is a slight difference in feel:

• lærer os dansk = teaches us Danish
• underviser os i dansk = teaches us in Danish / gives us instruction in Danish

Undervise is often a bit more formal or school-like.
Also notice the pattern changes:

• lære nogen noget
• undervise nogen i noget

So with undervise, you need i before the subject:

• Læreren underviser os i dansk.

Both are useful, but the structure is different.

Yes.

You can say:

• I klassen lærer læreren os dansk.

This is grammatical, but when you move i klassen to the front, the verb must still stay in second position, so lærer comes before læreren.

That is a very Danish feature.

Compare:

• Læreren lærer os dansk i klassen.
• I klassen lærer læreren os dansk.

Both are correct, but the emphasis changes a little.