Kennarinn segir að „hundur“ sé nafnorð og að „hlaupa“ sé sagnorð.

Kennari means teacher. The ending -inn is the suffixed definite article, so kennarinn means the teacher.

This is very common in Icelandic: instead of a separate word for the, the article is usually attached to the noun.

Here að means that and introduces a subordinate clause:

• Kennarinn segir að hundur sé nafnorð = The teacher says that hundur is a noun

So að is not the infinitive marker here; it is a conjunction meaning that.

Because there are two separate subordinate clauses:

• að hundur sé nafnorð
• að hlaupa sé sagnorð

Repeating að makes the structure clear and sounds very natural. Icelandic can sometimes leave out the second að if the sentence is clear enough, but keeping it is common and safe for learners.

Sé is the present subjunctive of vera (to be).

After verbs like segja (to say), Icelandic often uses the subjunctive in indirect speech or reported statements. So að hundur sé nafnorð is a normal way to report what someone says.

Very roughly:

• er = indicative, more straightforward factual statement
• sé = subjunctive, common in reported or dependent clauses like this

In everyday Icelandic, you may also hear er in some similar sentences, but sé is very natural here.

Because the sentence is talking about the words themselves, not using them in their ordinary meaning.

When Icelandic refers to a word as a word, it usually uses the citation or dictionary form:

• nouns: nominative singular → hundur
• verbs: infinitive → hlaupa

So the teacher is saying that the word hundur belongs to the class noun, and the word hlaupa belongs to the class verb.

Because this is the basic dictionary form of the noun, not the meaning the dog in an ordinary sentence.

Compare:

• hundur = dog as the basic noun form
• hundurinn = the dog

When you name a word as an example in grammar, Icelandic normally uses the basic citation form, so hundur is the expected choice.

Icelandic has no indefinite article. English says a noun and a verb, but Icelandic simply uses the noun by itself:

• nafnorð = a noun
• sagnorð = a verb

So sé nafnorð literally looks like is noun, but it naturally translates as is a noun.

They are in the nominative.

After vera (to be), predicate nouns are normally nominative in Icelandic. So the pattern is the same as in sentences like:

• Hann er kennari = He is a teacher

Likewise:

• hundur sé nafnorð
• hlaupa sé sagnorð

Both nafnorð and sagnorð function as predicate nouns.

Because this is a subordinate clause introduced by að.

In main clauses, Icelandic usually follows verb-second order:

• Kennarinn segir

But subordinate clauses do not follow the same pattern. After að, the subject or topic normally comes before the finite verb:

• að hundur sé nafnorð
• að hlaupa sé sagnorð

So this word order is exactly what you would expect in a dependent clause.

They are traditional Icelandic grammar terms:

• nafnorð = literally name-word → noun
• sagnorð = literally something like saying-word or predicate-word → verb

You do not need the literal meanings to use them correctly, but they can help you remember the terms.

That is a normal Icelandic punctuation style. Icelandic often uses low opening quotation marks and high closing quotation marks:

• „hundur“
• „hlaupa“

In digital writing, people may also use straight quotes, but „ ... “ is a standard printed style in Icelandic.