Samkvæmt lækninum er hann heilbrigður.

Because samkvæmt takes the dative case, so læknirinn changes form.

• læknirinn = the doctor in the nominative
• lækninum = the doctor in the dative

So after samkvæmt, you say:

• samkvæmt lækninum = according to the doctor

This is something you simply have to learn with the word samkvæmt: it is followed by the dative.

Samkvæmt means according to or in accordance with.

In this sentence, it introduces the source of the statement:

• Samkvæmt lækninum = According to the doctor

It is very commonly used when reporting information from a person, report, rule, law, or source.

Examples:

• Samkvæmt veðurspánni... = According to the weather forecast...
• Samkvæmt lögunum... = According to the law...

So here, it tells us that the claim comes from the doctor.

This is because Icelandic is a verb-second language in main clauses. That means the finite verb usually comes in the second position.

Here, the first element is:

• Samkvæmt lækninum

So the verb must come next:

• er

Then comes the subject:

• hann

So the structure is:

• Samkvæmt lækninum
  • er
    • hann
      • heilbrigður

This is very normal Icelandic word order. English speakers often expect the subject to come right before the verb, but Icelandic often puts some other element first and keeps the verb in second position.

Yes, that is also grammatical.

Both are possible, but the emphasis is slightly different:

• Samkvæmt lækninum er hann heilbrigður.
  This puts according to the doctor first, so the source is emphasized.

• Hann er heilbrigður samkvæmt lækninum.
  This starts more neutrally with he is healthy, then adds according to the doctor afterward.

So the original sentence is not the only possible word order, but it is a very natural one.

Because heilbrigður is an adjective agreeing with hann.

In Icelandic, adjectives usually agree with the noun or pronoun they describe in:

• gender
• number
• case

Here, hann means he, so the adjective must be:

• masculine
• singular
• nominative

That gives:

• heilbrigður

Compare:

• hann er heilbrigður = he is healthy
• hún er heilbrigð = she is healthy
• það er heilbrigt = it is healthy

So the ending changes depending on who or what is being described.

Because hann is the subject of the verb er.

In Icelandic, the subject of a sentence is usually in the nominative case. Even though hann comes after the verb here, it is still the subject.

So:

• hann = nominative subject
• er = is
• heilbrigður = adjective describing the subject

The unusual thing for an English speaker is mainly the word order, not the role of hann.

Yes. Er is the present tense singular form of the verb vera, which means to be.

So here:

• er = is

Examples:

• ég er = I am
• þú ert = you are
• hann er = he is
• við erum = we are

In this sentence, er links the subject hann with the description heilbrigður.

It is often treated like a preposition in learner materials because it behaves similarly: it combines with a noun phrase and requires a certain case, here the dative.

So for practical learning, it is perfectly fine to remember:

• samkvæmt
  • dative = according to

That is the key thing you need in order to use it correctly.

Usually it means healthy in the general sense, often physical health, but it can also be used more broadly depending on context.

For example, Icelandic can also use related expressions for things like:

• a healthy person
• a healthy habit
• a healthy attitude
• even a healthy economy in some contexts

In this sentence, because of lækninum, the most natural interpretation is physical or medical health.

The three biggest things are:

1. samkvæmt takes the dative

   • lækninum, not læknirinn

2. Icelandic main clauses often use verb-second word order

   • Samkvæmt lækninum er hann...

3. The adjective agrees with the subject

   • hann → heilbrigður

So this one sentence is a good example of:

• case after a preposition-like word,
• Icelandic word order,
• adjective agreement.