Þeir eru nánir vinir.

A natural approximate pronunciation is:

• Þeir ≈ thair
• eru ≈ EH-ru
• nánir ≈ NOW-neer or NAU-neer
• vinir ≈ VIH-neer

A few useful pronunciation points:

• Þ is like th in thing, not like th in this.
• ei in þeir is pronounced like ay in day.
• The á in nánir is a long vowel, somewhat like ow in now.
• Icelandic r is usually trilled or tapped.

So the whole sentence sounds roughly like: thair EH-ru NOW-neer VIH-neer.

Þeir means they.

It is the masculine plural form of they, so it is used:

• for a group of men
• or sometimes for a mixed-gender group

If the group were all women, Icelandic would use þær instead.

Eru is the present plural form of the verb að vera (to be).

So:

• ég er = I am
• þú ert = you are
• hann / hún / það er = he / she / it is
• við erum = we are
• þið eruð = you are
• þeir / þær / þau eru = they are

Since the subject is þeir (they), the verb must be eru.

Because nánir has to agree with the noun it describes.

The noun vinir (friends) is:

• plural
• masculine
• nominative

So the adjective must also be:

• plural
• masculine
• nominative

That gives nánir.

Very roughly, the adjective náinn (close) changes like this in the nominative:

• masculine singular: náinn
• feminine singular: náin
• neuter singular: náið
• masculine plural: nánir
• feminine plural: nánar
• neuter plural: náin

So nánir matches vinir.

Because the sentence is talking about more than one friend: friends.

The singular is:

• vinur = friend

The plural is:

• vinir = friends

So:

• Hann er náinn vinur. = He is a close friend.
• Þeir eru nánir vinir. = They are close friends.

Because vinir is the nominative plural, and here it is used as a predicate noun after the verb to be.

In Icelandic, after vera (to be), a noun like this is normally in the nominative:

• Þeir eru vinir. = They are friends.

Vini is a different case form, not the one needed here.

So both nánir and vinir are in the nominative plural to match the structure of the sentence.

Because Icelandic often does not use an article in the same way English does.

In this sentence, vinir simply means friends. English also has no article here:

• They are close friends.

If Icelandic wants to say the friend or the friends, it usually adds the definite article to the end of the noun:

• vinurinn = the friend
• vinirnir = the friends

But in Þeir eru nánir vinir, no definite article is needed.

Literally, náinn is related to the idea of being close or near, but in this sentence nánir vinir means close friends in the normal English sense.

So it describes a strong friendship, not physical distance.

Examples:

• Þeir eru vinir. = They are friends.
• Þeir eru nánir vinir. = They are close friends.

The normal, neutral word order is:

• Þeir = subject
• eru = verb
• nánir vinir = complement

So:

• Þeir eru nánir vinir.

Icelandic can sometimes change word order for emphasis or in special contexts, but for a learner this is the standard pattern to use.

Not in its current form.

Because þeir is masculine plural, this sentence refers to:

• men
• or a mixed group

If you wanted to say They are close friends about a group of women, you would use feminine plural forms:

• Þær eru nánar vinkonur.

That sentence uses:

• þær = they (feminine)
• nánar = close (feminine plural)
• vinkonur = female friends

So the forms change depending on gender.

The dictionary forms are:

• þeir → usually learned as part of the pronoun system of hann / hún / það and their plural forms
• eru → vera (to be)
• nánir → náinn (close)
• vinir → vinur (friend)

This is useful because Icelandic words change form a lot, so the exact word you see in a sentence is often not the dictionary form.

Yes.

In Þeir eru nánir vinir, the subject is þeir (they), and nánir vinir tells us what they are.

So:

• vinir is the main noun: friends
• nánir describes that noun: close

Together they form the complement of the sentence:

• They are close friends.

Yes, everything is plural where it needs to be:

• Þeir = they → plural
• eru = are → plural verb form
• nánir = close → plural adjective
• vinir = friends → plural noun

This is a good example of Icelandic agreement: words change form so they match each other.