Afhendingardagurinn er á morgun.

Because Icelandic very often makes compound nouns by joining words together.

Here, Afhendingardagurinn is built from:

• afhending = delivery
• dagur = day

These combine into afhendingardagur = delivery day.

Then the definite ending is added, giving afhendingardagurinn = the delivery day.

So what looks like one huge word is often just a compound plus the definite article.

That -ar- is a very common Icelandic compound feature.

The noun afhending has the genitive form afhendingar. In compounds, Icelandic often uses the genitive of the first noun as a linking form. So:

• afhending → afhendingar-
• dagur = day

That gives afhendingardagur.

You can think of it loosely as something like day of delivery, although in English we usually translate it more naturally as delivery day.

Not every compound works in exactly the same way, but this pattern is very common.

Because the base noun is dagur and here it is:

• singular
• definite
• nominative (because it is the subject of the sentence)

The indefinite form is:

• dagur = a day

The definite nominative singular form is:

• dagurinn = the day

In the compound, the same thing happens:

• afhendingardagur = a delivery day
• afhendingardagurinn = the delivery day

So -urinn is not random; it is the normal definite form of dagur in this position.

Because Icelandic usually expresses the by attaching it to the end of the noun instead of putting a separate word before it.

So instead of something like the day, Icelandic often says:

• dagurinn

And instead of the delivery day, it says:

• afhendingardagurinn

There is also a separate demonstrative/article-like word in Icelandic, but in ordinary sentences like this, the suffixed definite article is the normal choice.

Á morgun is the normal Icelandic expression for tomorrow.

It is best learned as a fixed time phrase, just like:

• í dag = today
• í gær = yesterday
• á morgun = tomorrow

Even though á is usually a preposition meaning things like on or at, in this expression you should mostly treat á morgun as a set phrase rather than translating it word by word.

No, this is a very normal Icelandic sentence pattern:

• Afhendingardagurinn = subject
• er = verb
• á morgun = time expression

So the structure is basically:

Subject + verb + time phrase

This is the neutral, straightforward order.

You can also move the time expression to the front for emphasis:

• Á morgun er afhendingardagurinn.

When you do that, Icelandic keeps the verb in second position, which is a very important word-order rule in the language.

Usually not for this meaning.

Afhendingardagurinn refers to a specific, known delivery day: the delivery day.

If you say Afhendingardagur er á morgun, it sounds indefinite, like a delivery day is tomorrow, which is not natural in most contexts.

So in an ordinary sentence about a specific scheduled day, the definite form is the right choice:

• Afhendingardagurinn er á morgun.

Because Icelandic, like English, often uses the present tense for scheduled future events or fixed arrangements.

So er á morgun works like English sentences such as:

• The meeting is tomorrow.
• The exam is tomorrow.

It is not strange at all. It sounds natural and idiomatic.

You could sometimes use a future form in other contexts, but here the present tense is exactly what you would expect.

A yes/no question is made by putting the verb first:

• Er afhendingardagurinn á morgun?

A negative sentence uses ekki:

• Afhendingardagurinn er ekki á morgun.

This is a very useful pattern to remember:

• statement: X er ...
• question: Er X ...?
• negative: X er ekki ...