Lokaatriðið er í handritinu en ekki í stiklunni.

It is a compound noun, which is very common in Icelandic. It is built from:

• loka- = final, closing
• atriði = scene, item, moment

Icelandic usually writes compounds as one word, so you get lokaatriði rather than two separate words.

The aa is just the result of joining the two parts:

• loka
  • atriði → lokaatriði

Nothing special is happening beyond that; both vowels stay.

In Icelandic, the definite article is usually attached to the end of the noun instead of being a separate word.

So in this sentence:

• lokaatriðið = the final scene
• handritinu = in the script
• stiklunni = in the trailer

That is why you do not see a separate standalone word like English the.

Er is the present tense form of að vera, meaning to be.

Here it means is.

Because the subject Lokaatriðið is singular, er is the correct singular form.

Because both nouns come after í, and here í is being used for location, so it takes the dative case.

That gives you:

• handrit → handritinu
• stikla → stiklunni

These are also definite forms, so they include the sense of the as well.

A useful way to think about it is:

• base noun + case ending + definite article ending

This is a very important Icelandic pattern:

• í + dative = location, being in something
• í + accusative = motion into something

So:

• í handritinu = located in the script
• if something were moving into the script, Icelandic would use the accusative instead

In this sentence, nothing is moving anywhere. The sentence is just stating where something is found, so dative is used.

En means but, and ekki means not.

Together, en ekki creates a contrast:

• ... en ekki ... = ... but not ...

So the sentence first says where the final scene is, and then contrasts that with where it is not.

Because the second part is still a full prepositional phrase:

• í handritinu
• í stiklunni

The negation applies to the whole phrase í stiklunni, so repeating í is the normal and natural Icelandic structure.

In other words, Icelandic does not normally say the equivalent of in the script but not the trailer here. It keeps the preposition with both parts.

They are:

• lokaatriði — neuter
• handrit — neuter
• stikla — feminine

This matters because gender and case affect the endings.

For example:

• neuter handrit becomes handritinu
• feminine stikla becomes stiklunni

Knowing the dictionary form helps you recognize how the sentence form was built.

Usually, yes, in this kind of context. Stikla is a promotional preview for a film, show, or similar media.

Depending on context, English might sometimes say trailer or teaser, but trailer is the most natural match in many cases.

It is also useful to remember that stikla is a feminine noun, which helps explain the form stiklunni here.

Yes, it is very normal.

The structure is:

• Lokaatriðið — subject
• er — verb
• í handritinu — prepositional phrase
• en ekki í stiklunni — contrasting phrase

So this is a straightforward Icelandic sentence with standard word order.