Umgengnisreglurnar eru skýrar.

Because Icelandic makes very frequent use of compound nouns. What English often writes as multiple words, Icelandic often combines into one.

Here, umgengnisreglurnar is basically built from:

• umgengnis- = relating to conduct / behavior / interaction
• reglur = rules
• -nar = the (definite article, feminine plural)

So Icelandic treats the whole idea as one noun: the conduct rules / the rules of conduct.

A useful breakdown is:

• umgengni = conduct, behavior, interaction
• umgengnis- = a compound form based on the genitive of umgengni
• regla = rule
• reglur = rules
• reglurnar = the rules
• umgengnisreglurnar = the rules of conduct / the conduct rules

So the main noun is regla. That means the whole compound behaves grammatically like regla: it is feminine.

In Icelandic, the definite article is usually attached to the end of the noun instead of standing alone as a separate word.

So:

• reglur = rules
• reglurnar = the rules

In this sentence, -nar is the definite article ending. That is why you do not see a separate word like English the.

Because the subject is plural.

• er = is
• eru = are

Since umgengnisreglurnar means the rules (plural), the verb must also be plural:

• Umgengnisreglan er skýr. = The rule is clear.
• Umgengnisreglurnar eru skýrar. = The rules are clear.

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

Here, the subject is:

• reglur / reglurnar = feminine plural

So the adjective skýr must appear in the feminine plural nominative form:

• skýr = clear (dictionary form)
• skýrar = clear, feminine plural nominative

That is why the sentence has:

• Umgengnisreglurnar eru skýrar.

not:

• Umgengnisreglurnar eru skýr.

It is nominative, because it is the subject of the sentence.

The basic structure is:

• Umgengnisreglurnar = subject
• eru = verb
• skýrar = predicate adjective

Since the subject is nominative, the adjective after vera (to be) also appears in the matching nominative form: skýrar.

Yes. In many Icelandic compounds, the first element appears in a form that comes from the genitive.

Here:

• umgengni = conduct / behavior / interaction
• genitive singular = umgengnis

That -s form is then used before the second noun:

• umgengnis + regla → umgengnisregla

This is very common in Icelandic compounds.

It would be:

• Umgengnisreglan er skýr.

Breakdown:

• umgengnisreglan = the rule of conduct
• er = is
• skýr = clear

Notice how everything changes to singular:

• reglurnar → reglan
• eru → er
• skýrar → skýr

Yes, this is a very normal and straightforward order:

• Subject + verb + adjective/complement

So:

• Umgengnisreglurnar = subject
• eru = are
• skýrar = clear

This is very similar to English in this kind of sentence.

Icelandic word order can change for emphasis, especially because main clauses follow a verb-second pattern, but this version is the most neutral and natural one for a learner to use.

A simple learner-friendly guide is:

• Umgengnisreglurnar: stress the first syllable: UM-geng-nis-reglurnar
• eru: roughly EH-ru
• skýrar: stress SKÝ: SKEER-ar

A few useful points:

• Icelandic usually stresses the first syllable of a word.
• ý is a long vowel sound, roughly like ee.
• r is pronounced more clearly than in most English accents.

You do not need perfect pronunciation right away, but keeping the stress on the first syllable will help a lot.