Brottfarardagurinn er á morgun.

Because Icelandic, like the other North Germanic languages, very often writes compound nouns as a single word.

brottfarardagurinn is built from:

• brottför = departure
• dagur = day

In the compound, the first part appears as brottfarar-, which comes from the genitive form of brottför. So the base compound brottfarardagur is literally departure-day or more naturally day of departure.

The base form is brottfarardagur.

The ending -inn / -urinn is the suffixed definite article, so:

• brottfarardagur = a departure day / departure day
• brottfarardagurinn = the departure day

Since the last part of the compound is dagur, that is the part that carries the grammatical ending and the article.

Because dagur is a masculine noun, and in the nominative singular definite form it becomes dagurinn.

The same pattern happens inside the compound:

• dagur = day
• dagurinn = the day
• brottfarardagur = departure day
• brottfarardagurinn = the departure day

So the -urinn ending is not random; it is the normal definite ending for this noun pattern.

Er is the 3rd person singular present tense of vera, the verb to be.

So here it simply means is.

Because brottfarardagurinn is singular, Icelandic uses singular er:

• ég er = I am
• þú ert = you are
• hann/hún/það er = he/she/it is

Because á morgun is a fixed time expression in Icelandic.

Word-for-word, á often means something like on or at, but in this expression you should learn á morgun as a whole unit meaning tomorrow.

It is similar to other common time expressions:

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

So even if it does not match English word-for-word, it is completely normal Icelandic.

Not in this sentence.

In the expression á morgun, morgun means tomorrow.

The usual word for morning is morgunn.

So:

• á morgun = tomorrow
• í morgun can mean this morning in the right context
• morgunn = morning

This is a place where Icelandic uses closely related forms that English speakers can easily mix up.

It is in the nominative singular definite.

That is because it is the subject of the sentence:

• Brottfarardagurinn = the subject
• er = is
• á morgun = tomorrow

In Icelandic compounds, the case and article ending are added to the final part of the compound, here dagur.

Yes. That is good Icelandic too.

Both of these are possible:

• Brottfarardagurinn er á morgun.
• Á morgun er brottfarardagurinn.

The difference is mainly emphasis. If you start with Á morgun, you highlight the time more strongly.

This also shows an important Icelandic pattern: the finite verb often stays in second position. So when a time expression comes first, the verb still comes next.

A rough English-friendly approximation is BROHT-fa-ra-da-gu-rin.

A few helpful pronunciation notes:

• Stress is on the first syllable: BROTT-
• tt in brott often sounds a bit like ht to English ears
• The r sounds should be tapped or lightly rolled
• The final -urinn is lighter and shorter than an English speaker might expect

This is only an approximation, but it can help you get started.

Not exactly, though they are close.

• Brottförin er á morgun = The departure is tomorrow
• Brottfarardagurinn er á morgun = The departure day is tomorrow

The first sentence focuses on the event of leaving.
The second focuses on the day associated with departure.

Depending on context, one may sound more natural than the other. If you are talking about a schedule or travel plan, brottfarardagurinn can make perfect sense.