Meðferðin er mikilvæg.

Meðferðin is meðferð + -in.

• meðferð = treatment
• -in = the definite article, meaning the

So meðferðin means the treatment.

This is very common in Icelandic: instead of using a separate word like English the, Icelandic usually adds the article to the end of the noun.

• meðferð = treatment
• meðferðin = the treatment

In normal Icelandic, the definite article is usually a suffix, so it gets attached to the noun.

That means:

• meðferðin = the treatment

There is also a separate form like hinn / hin / hið, but that is used much less often and usually in more formal, literary, or special grammatical contexts.

So for everyday Icelandic, meðferðin is the natural form.

Meðferð is a feminine noun.

You often just have to learn noun gender as part of the vocabulary item, but in this sentence you can also see it from the adjective:

• mikilvægur = masculine
• mikilvæg = feminine
• mikilvægt = neuter

Since the sentence uses mikilvæg, that matches a feminine singular noun, so meðferðin is feminine.

Because Icelandic adjectives must agree with the noun they describe in gender, number, and case.

Here:

• meðferðin is feminine
• it is singular
• it is the subject, so it is in the nominative

So the adjective must also be feminine singular nominative:

• mikilvæg

Compare:

• bíllinn er mikilvægur = the car is important (masculine)
• meðferðin er mikilvæg = the treatment is important (feminine)
• húsið er mikilvægt = the house is important (neuter)

In this sentence, mikilvæg is a predicate adjective, not an adjective directly in front of the noun.

The structure is:

• Meðferðin = the treatment
• er = is
• mikilvæg = important

So the whole sentence means:

• The treatment is important.

If you wanted to say the important treatment, the structure would be different, because the adjective would directly modify the noun.

Er means is.

It is the 3rd person singular present tense of the verb vera (to be).

So:

• ég er = I am
• þú ert = you are
• hann / hún / það er = he / she / it is

In Meðferðin er mikilvæg, er links the subject and the adjective, just like English is.

It is in the nominative singular.

That is because it is the subject of the sentence:

• The treatment is important.

In simple X is Y sentences, the subject is normally in the nominative.

So:

• meðferðin = nominative singular definite

This is a very good question, because Icelandic adjectives can have strong and weak forms.

After the verb vera (to be), predicate adjectives are normally in the strong form, even when the noun is definite.

So:

• Meðferðin er mikilvæg. not a weak adjective form here.

In other words, the definiteness is shown by meðferðin (the treatment), while mikilvæg stays in the normal predicate form.

A rough guide for an English speaker is:

MEH-thfer-thin er MIH-kil-vyeg

A few important notes:

• ð in meðferðin is like the th in this
• þ would be like the th in thing, but this sentence has ð, not þ
• r is usually rolled or tapped
• the stress in Icelandic is normally on the first syllable of a word:
  • MEÐferðin
  • MIKilvæg

The exact pronunciation of æ in mikilvæg can be tricky for English speakers, but it is roughly like eye or ye in many contexts.

Not always.

Meðferð can mean:

• treatment in a medical sense
• handling
• processing
• sometimes treatment of a topic or issue

So the exact meaning depends on context. In many learning examples, it will often be understood as treatment.

Yes. This is the most straightforward, normal word order:

• Subject + verb + complement
• Meðferðin
  • er
    • mikilvæg

That is exactly parallel to English:

• The treatment is important.

Icelandic can change word order in some contexts, especially because of the verb-second rule, but this sentence is the basic neutral order.

You could, but it would sound more marked, literary, or emphatic.

The neutral everyday sentence is:

• Meðferðin er mikilvæg.

If you put mikilvæg first, you are emphasizing it more strongly, something like:

• Important is the treatment or
• It is the treatment that is important

So for normal usage, stick with:

• Meðferðin er mikilvæg.

The indefinite version would be:

• Meðferð er mikilvæg.

That means:

• Treatment is important or
• A treatment is important, depending on context

The difference is:

• meðferð = treatment / a treatment
• meðferðin = the treatment

So the suffix -in is what makes it definite.