Skilakassinn er fyrir utan.

The dictionary form is skilakassi.

That is the indefinite singular form, meaning something like a return box / drop-off box.
The form in the sentence, skilakassinn, is the definite form: the return box.

A useful learner habit in Icelandic is: if a noun seems to end in something like -inn, -in, or -ið, try looking it up without that ending.

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

So:

• skilakassi = a return box
• skilakassinn = the return box

In this sentence, -inn is the ending that marks the noun as definite.

This is one of the biggest differences from English. Instead of saying the box, Icelandic often says something more like box-the.

It is a compound noun:

• skila- = related to skila, to return / hand in
• kassi = box
• -inn = the

So the structure is basically:

• skila + kassi → skilakassi = return box / drop box
• skilakassi + definite ending → skilakassinn = the return box

Icelandic uses compounds very often, much more freely than English does.

Because Icelandic normally writes compound nouns as one word.

So English might write:

• return box
• drop box

But Icelandic prefers a single compound:

• skilakassi

Then the definite ending is added to the whole compound:

• skilakassinn

This is completely normal in Icelandic spelling.

Here it is:

• singular
• masculine
• nominative
• definite

It is in the nominative because it is the subject of the sentence:

• Skilakassinn = the thing being talked about
• er = is
• fyrir utan = outside

So, grammatically, skilakassinn is the subject in the ordinary subject position.

Er is the present tense of vera, the verb to be.

So here:

• er = is

This is a very common verb, and you will see er constantly in Icelandic.

In this sentence it links the subject to its location:

• Skilakassinn er fyrir utan.
• The return box is outside.

Here, fyrir utan means outside.

In this sentence it works as a location expression telling you where the box is.

A helpful thing to know is that fyrir utan can also be used with a noun after it, for example:

• fyrir utan húsið = outside the house

So in your sentence, the noun after it is simply omitted because the meaning is already clear from context: just outside.

Also, in other contexts, fyrir utan can mean things like besides or except for, so context matters.

Because it is a fixed expression made of two parts:

• fyrir
• utan

Together, they form a common phrase meaning outside / outside of.

English learners sometimes want to treat it as a single adverb, but in Icelandic it is normally written as two words.

So it is best to learn fyrir utan as a unit.

Sometimes yes, depending on context, but they are not always identical.

• úti often means outside / outdoors / out
• fyrir utan often means outside (of a place/building)

So Skilakassinn er úti might work in some situations, but Skilakassinn er fyrir utan more clearly suggests that it is outside the place being discussed.

A rough contrast:

• Hann er úti. = He is outside / outdoors.
• Hann er fyrir utan húsið. = He is outside the house.

In your sentence, fyrir utan is a natural choice.

No, this is a very straightforward Icelandic sentence.

It follows the basic pattern:

• Subject + verb + location
• Skilakassinn + er + fyrir utan

That is very similar to English:

• The return box + is + outside

So this sentence is a good example of simple, neutral word order.

A rough pronunciation guide is:

SKEE-la-khat-sin er FEE-rir Ü-tan

A few notes:

• sk before a front vowel in Icelandic is not exactly like English sk
• k in kassi is aspirated, a bit like kh
• r is usually a tapped or rolled Icelandic r
• the u in utan is not a normal English oo sound; it is closer to a rounded i/ü sound

If you want a very rough syllable breakdown:

• Ski-la-kass-inn
• er
• fyr-ir
• ut-an

The main stress in Icelandic is usually on the first syllable of the word.