Þáttaröðin var miðlungs, en endirinn var snilld.

Þáttaröðin means the TV series.

The base word is þáttaröð, which is a compound noun meaning series of episodes, so in normal usage it often means a TV series or miniseries. The ending -in is the definite article, so þáttaröðin = the TV series.

Literally, the compound is built from words related to episodes and a series/sequence.

In Icelandic, the is usually attached to the noun as a suffix.

So:

• þáttaröð = TV series
• þáttaröðin = the TV series

and

• endir = ending
• endirinn = the ending

This is one of the biggest differences from English. Instead of a separate article before the noun, Icelandic usually adds it to the end.

They are in the nominative singular.

That is because they are the subjects of the verb var:

• Þáttaröðin var miðlungs
• endirinn var snilld

Both the TV series and the ending are the things being described, so nominative is the expected case here.

Miðlungs means something like average, middling, so-so, or mediocre.

In this sentence, it is slightly negative. It does not usually mean medium-sized here. So the idea is not that the series was in the middle in size or length, but that its quality was only average.

A natural English sense is often:

• average
• nothing special
• mediocre

Miðlungs is commonly used as a fixed form in this kind of sentence.

Many Icelandic adjectives change for gender, number, and case, but miðlungs often appears unchanged when it means average/mediocre. So even though þáttaröðin is feminine singular, miðlungs still stays miðlungs.

That can feel unusual to an English speaker who is expecting a more regular adjective pattern.

Icelandic often uses snilld, a noun meaning genius, brilliance, or masterpiece-level excellence, in a very natural way after vera.

So:

• endirinn var snilld

is literally close to the ending was genius or the ending was brilliance.

But in natural English, you would usually translate it as:

• the ending was brilliant
• the ending was amazing
• the ending was pure genius

So yes, it is a noun, but it works very naturally in Icelandic.

Because this sentence has two separate clauses joined by en:

• Þáttaröðin var miðlungs
• en endirinn var snilld

Each clause needs its own verb, just like in English:

• The series was mediocre, but the ending was brilliant

So repeating var is completely normal.

En means but.

After en, the second clause starts normally again. Here the word order is straightforward:

• endirinn = subject
• var = verb
• snilld = complement

So en itself does not force anything strange here. The second clause is just a normal main clause.

Because en is joining two full clauses, each with its own subject and verb.

So the structure is:

• Þáttaröðin var miðlungs
• endirinn var snilld

When two complete clauses are joined with en, a comma is very normal.

Var is the past tense of vera, so it means was.

If you said:

• Þáttaröðin er miðlungs, en endirinn er snilld

that would mean The TV series is mediocre, but the ending is brilliant.

Both can be possible depending on context, but var presents the opinion as something about a watched, completed experience: you watched it, and this was your judgment.

The most important ones here are:

• Þ / þ = th in thing
• ð = th in this
• á = roughly like ow in cow
• í = roughly like ee in see

So for a rough English-friendly guide:

• Þáttaröðin ≈ THOWT-ta-rur-thin
• miðlungs ≈ MITH-lungs
• endirinn ≈ EN-di-rin

These are only rough approximations, but they help you get close.

Not in normal Icelandic.

Without the definite endings, that would sound unnatural here, because you are clearly talking about a specific series and its specific ending. Icelandic strongly prefers the definite forms in this kind of sentence:

• þáttaröðin = the series
• endirinn = the ending

So the definite suffixes are important here.