Safnkosturinn er stór.

Because Icelandic usually puts the definite article on the end of the noun instead of using a separate word.

• safnkostur = collection, holdings
• safnkosturinn = the collection, the holdings

So the ending -inn is doing the job that the does in English.

The base noun is safnkostur.

Then the definite article is added, giving safnkosturinn.

A helpful way to see it:

• safnkostur = indefinite form
• safnkostur + inn → safnkosturinn = definite form

In practice, the exact shape of the ending can look slightly different depending on the noun, but for a learner, the key point is that -inn marks the here.

Er means is.

It is the present tense, third person singular form of the verb vera (to be).

So:

• Safnkosturinn = the collection
• er = is
• stór = large

This is a very basic Icelandic sentence pattern:

subject + er + adjective

Examples:

• Húsið er stórt. = The house is big.
• Bókin er góð. = The book is good.

Because Icelandic adjectives agree with the noun in gender, number, and often case.

Here, safnkosturinn is:

• singular
• masculine
• nominative

So the adjective appears in the matching form:

• masculine singular nominative: stór

Compare:

• stór = masculine singular nominative
• stór = feminine singular nominative
• stórt = neuter singular nominative

So if the noun were neuter, you would expect stórt instead.

Because in this sentence stór is a predicative adjective. That means it comes after er and describes the subject.

In Icelandic, predicative adjectives usually do not take a separate definite form just because the noun is definite.

So:

• Safnkosturinn er stór. = The collection is large.

But when an adjective comes directly before a noun, the pattern is different:

• stóri safnkosturinn = the large collection

So the difference is:

• Safnkosturinn er stór. = the collection is large
• stóri safnkosturinn = the large collection

It is in the nominative case.

That is because it is the subject of the sentence. In simple statements like this, the subject is normally nominative.

So:

• Safnkosturinn = nominative singular definite
• er stór = is large

Yes, it is a compound noun.

It is built from:

• safn = collection, museum, archive, gathering
• kostur = stock, selection, holdings, resources, option (depending on context)

Together, safnkostur refers to the holdings or collection of something such as a library, museum, or archive.

Compound words are extremely common in Icelandic, so it is useful to get used to spotting them.

The normal order here is:

subject + verb + adjective

So:

• Safnkosturinn = subject
• er = verb
• stór = complement/adjective

This is the most straightforward word order for a simple statement.

You may sometimes see other orders in Icelandic for emphasis or because of sentence structure, but this sentence is the plain, neutral version.

You would use the indefinite noun:

Safnkostur er stór.

That means A collection is large or Collection holdings are large, depending on context, though in real usage the definite version often sounds more natural if a specific collection is meant.

The main change is:

• safnkosturinn = the collection
• safnkostur = a collection / collection

You add ekki (not):

Safnkosturinn er ekki stór.

That means The collection is not large.

The basic pattern is:

subject + er + ekki + adjective

A rough learner-friendly guide would be:

• Safnkosturinn ≈ SAHVN-kos-tu-rin
• er ≈ ehr
• stór ≈ store (but with a rolled/trilled r if possible)

A few useful pronunciation notes:

• fnk in Safnkosturinn can feel a bit crowded for English speakers; say it slowly at first.
• ó is a long vowel, roughly like o in go, though not exactly the same.
• Icelandic r is usually trilled or tapped, not the English r.

If you want to sound more natural, listening to native audio is especially helpful with words like safnkosturinn, because long compounds are very common in Icelandic.