Legen kontrollerer hjertet.

Because legen is the definite singular form of lege.

• lege = doctor / a doctor
• legen = the doctor

In Norwegian, the definite article is usually attached to the end of the noun instead of being a separate word like English the.

Since lege is a common-gender noun, its definite singular ending is -en:

• en lege = a doctor
• legen = the doctor

Because hjertet is the definite singular form of hjerte.

• et hjerte = a heart
• hjertet = the heart

Hjerte is a neuter noun, so in the definite singular it usually takes -et:

• et hus → huset
• et hjerte → hjertet

So Legen kontrollerer hjertet uses the doctor and the heart, not a doctor and a heart.

No. In this sentence, the is built into the nouns:

• legen = the doctor
• hjertet = the heart

That is very common in Norwegian.

However, if there is an adjective, Norwegian often uses double definiteness:

• legen = the doctor
• den flinke legen = the skilled doctor

So in simple cases, no separate the is needed, but with adjectives you often get both a separate definite word and a noun ending.

Kontrollerer is the present tense of the verb å kontrollere.

• å kontrollere = to check / to examine / to inspect / to monitor, depending on context
• kontrollerer = checks / is checking / examines / is examining

In Norwegian, the present tense is often formed by adding -er to the infinitive:

• å snakke → snakker
• å kontrollere → kontrollerer

The sentence can therefore mean something like:

• The doctor checks the heart
• The doctor is checking the heart

The exact English tense depends on context.

Not usually in this medical sentence.

Although å kontrollere can sometimes look like English to control, in many contexts it means:

• to check
• to examine
• to inspect
• to monitor

So in Legen kontrollerer hjertet, the most natural English idea is probably:

• The doctor checks the heart
• The doctor examines the heart

This is a good example of a word that looks familiar to English speakers but is not always used in exactly the same way.

The sentence uses the normal subject–verb–object order:

• Legen = subject
• kontrollerer = verb
• hjertet = object

So:

• Legen kontrollerer hjertet.
• The doctor checks the heart.

This is the most straightforward word order in a Norwegian main clause.

Yes, often it would.

Norwegian main clauses follow the V2 rule, which means the finite verb usually comes in the second position.

For example:

• Legen kontrollerer hjertet i dag. = The doctor checks the heart today.
• I dag kontrollerer legen hjertet. = Today, the doctor checks the heart.

Notice that when I dag comes first, the verb kontrollerer still stays in second position, so legen moves after the verb.

That is very important in Norwegian sentence structure.

The nouns have different grammatical genders:

• lege is common gender
• hjerte is neuter

This matters because the gender affects articles and endings.

For lege:

• en lege
• legen

For hjerte:

• et hjerte
• hjertet

So the endings in the sentence are not random; they reflect the noun genders.

A useful learner-level approximation is:

• hjertet ≈ YER-teh or HYER-teh, depending on accent and how detailed you want to be

A few important points:

• The hj- at the start is usually pronounced with a y-like sound, not a strong English h
• The final -et is often pronounced lightly, not as a full English et

So English speakers should be careful not to say a hard h-j combination.

A simple approximation is:

• legen ≈ LAY-gen or LEH-gen, depending on accent

The main thing is that it is a two-syllable word, and the ending -en is a normal definite ending.

If you are learning pronunciation, it is best to listen to native audio, because Norwegian vowel quality can be hard to represent exactly in English spelling.

Yes, you can say doktoren, but legen is usually the more standard and common word for the doctor in this kind of sentence.

• legen = the doctor
• doktoren = the doctor

In many everyday and medical contexts, lege is the more typical Norwegian word.

Also note:

• doctor as a profession in English can mean different things
• lege specifically means a medical doctor

Because in Norwegian, common nouns are not capitalized.

So you write:

• legen
• hjertet

not capitalized, unless they come at the beginning of a sentence.

Only the first word of the sentence is capitalized here because it starts the sentence:

• Legen kontrollerer hjertet.

This is different from German, where all nouns are capitalized.