Góð samskipti styrkja vináttuna.

Because góð has to agree with samskipti.

The noun samskipti is neuter plural, so the adjective góður changes to the matching form góð. In this sentence, góð samskipti is the subject, so the phrase is nominative neuter plural.

So:

• góður = masculine singular
• góða = some other gender/case combinations
• góð = the correct form here

That is a very common question. Samskipti is normally a plural noun in Icelandic. It often refers to communication, interactions, contact, dealings, or relations between people.

So even though English often uses a singular word like communication, Icelandic naturally uses the plural samskipti.

You can think of it as something like interactions or communications, even when English would not say it that way.

Here it is nominative, because it is the subject of the sentence: the thing doing the strengthening.

That said, the form samskipti can look the same in nominative and accusative plural. That is normal for many neuter nouns in Icelandic. So you often have to decide from the sentence structure, not just from the ending.

In Góð samskipti styrkja vináttuna, the structure is:

• Góð samskipti = subject
• styrkja = verb
• vináttuna = object

No. Here styrkja is a finite verb, specifically 3rd person plural present tense: they strengthen.

It happens to look exactly like the infinitive styrkja (to strengthen). That can be confusing for learners.

You can tell it is a present-tense verb here because it has a subject:

• Góð samskipti styrkja ... = Good communication / good interactions strengthen ...

If it were the infinitive, you would normally expect að styrkja = to strengthen.

Vináttuna is the accusative singular definite form of vinátta (friendship).

There are two things happening:

• the verb styrkja takes a direct object in the accusative
• the noun is definite, so it includes the attached article: -na

So:

• vinátta = friendship
• vináttu = friendship, in the accusative
• vináttuna = the friendship, in the accusative

Yes. Góð samskipti styrkja vináttu is grammatically possible, but the meaning changes slightly.

• vináttuna = the friendship / a specific friendship / friendship understood from context
• vináttu = friendship in a more general or indefinite sense

So the original sentence feels a bit more concrete, while vináttu would sound more general.

Because the sentence is making a general statement. Icelandic often leaves a noun indefinite in this kind of broad, general truth.

So góð samskipti means good communication / good interactions, not the good communication.

If you wanted to make it definite, you would use something like:

• góðu samskiptin = the good communications/interactions

Notice that with a definite noun phrase, the adjective also changes form.

It is broader than just spoken communication.

Depending on context, samskipti can mean:

• communication
• interaction
• contact
• dealings
• relations between people

In this sentence, it suggests healthy interpersonal communication and interaction. So English translations like Good communication strengthens friendship or Good interactions strengthen friendship both capture the idea.

The given order is the most neutral and natural one:

• Góð samskipti = subject
• styrkja = verb
• vináttuna = object

So this is standard subject–verb–object order.

Icelandic word order can change for emphasis, style, or focus, because the cases help show what each word is doing. For example, a different order may still be understandable. But for a learner, the original sentence is the safest and most natural version to use.