Orsökin er mikilvæg.

The base form is orsök, which means cause.

Orsökin = orsök + the suffixed definite article, so it means the cause.

In Icelandic, the definite article is usually attached to the noun as an ending instead of being written as a separate word.

So:

• orsök = cause
• orsökin = the cause

That -in ending is the definite article here.

Orsök is a feminine noun.

That matters because gender affects:

• the form of the definite article
• the form of adjectives that go with the noun
• other grammatical endings in different cases

In this sentence, the feminine gender helps explain why the adjective appears as mikilvæg.

It is in the nominative singular.

That is because orsökin is the subject of the sentence: it is the thing that is important.

So the structure is:

• Orsökin = subject, nominative singular
• er = is
• mikilvæg = predicate adjective describing the subject

Because the adjective must agree with the noun it describes.

Here, orsökin is:

• feminine
• singular
• nominative

So the adjective takes the matching form mikilvæg.

Compare:

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

So Orsökin er mikilvæg is correct because orsök is feminine.

The dictionary form is usually mikilvægur.

Icelandic adjectives are often listed in the masculine singular nominative form in dictionaries. So even though the sentence has mikilvæg, you would normally look it up as mikilvægur.

Because mikilvæg is a predicate adjective here: it comes after er and describes the subject.

In Icelandic, predicate adjectives usually appear in the regular agreeing form, not in the kind of form you might expect from an adjective placed directly before a definite noun.

So:

• Orsökin er mikilvæg = The cause is important

That is normal Icelandic grammar.

This sentence uses the most basic and natural order:

• Orsökin = subject
• er = verb
• mikilvæg = complement

So it follows a simple Subject–Verb–Complement pattern.

However, Icelandic is more flexible than English in some contexts. You can move elements for emphasis, but in a plain statement like this, Orsökin er mikilvæg is the normal order.

A rough English-friendly guide would be something like:

OR-suh-kin er MIH-kil-vigh

A few helpful notes:

• Stress usually falls on the first syllable of Icelandic words.
• ö is not the same as English o; it is closer to the vowel in German ö or French eu.
• The final sound in mikilvæg is not exactly like a hard English g.

This kind of spelling-based guide is only approximate, but it can help you get started.

You would say:

Orsökin er ekki mikilvæg.

Here ekki means not.

So the pattern is very simple:

• Orsökin er mikilvæg. = The cause is important.
• Orsökin er ekki mikilvæg. = The cause is not important.

Yes. Then you would usually use the indefinite noun:

Orsök er mikilvæg.

That means A cause is important or sometimes Cause is important, depending on context.

The main difference is:

• orsök = a cause
• orsökin = the cause