Viðbótin við skýrsluna er stutt.

It breaks down like this:

• Viðbótin við skýrsluna = the subject, literally the addition to the report
• er = is
• stutt = the predicate adjective, short

So the sentence structure is:

[subject] + [verb] + [adjective]

A more literal word-for-word layout is:

The addition to the report is short.

The ending -in is the suffixed definite article, which often corresponds to English the.

• viðbót = addition
• viðbótin = the addition

Icelandic usually attaches the to the end of the noun instead of putting it in front as a separate word.

Here, viðbótin is in the nominative singular because it is the subject of the sentence.

Because the preposition við takes the accusative case in this sentence.

Compare:

• skýrsla = report
• skýrslan = the report, nominative
• skýrslu = report, accusative
• skýrsluna = the report, accusative

Since the phrase is við skýrsluna, the noun has to be in the accusative. That is why you see -una instead of -an.

Here við means something like to, attached to, or in relation to.

So viðbót við skýrsluna means:

• an addition to the report
• a supplement to the report
• an addendum to the report

This is a good reminder that Icelandic prepositions do not always match English prepositions one-to-one. Even though við often has other meanings in other contexts, here it is the normal preposition used with viðbót.

Because adjectives in Icelandic agree with the noun they describe, and here stutt is agreeing with viðbótin, which is feminine singular.

The adjective comes from stuttur = short. Its nominative singular forms are:

• masculine: stuttur
• feminine: stutt
• neuter: stutt

So even though stutt may look like a neuter form, it is also the correct feminine nominative singular form in this adjective pattern.

Since viðbótin is feminine singular and the adjective is used predicatively after er, stutt is correct.

It is part of the full subject phrase.

The subject is not just viðbótin. The whole noun phrase is:

viðbótin við skýrsluna = the addition to the report

So við skýrsluna is modifying viðbótin, telling you what the addition is connected to.

That means the sentence is not:

• The addition is short, near the report

It is:

• The addition to the report is short

Icelandic handles articles differently from English.

For the, Icelandic usually uses a suffix attached to the noun:

• viðbótin = the addition
• skýrsluna = the report in the accusative

For a/an, Icelandic normally has no article at all:

• viðbót = an addition
• skýrsla = a report

So English uses separate words, but Icelandic often shows definiteness by changing the noun ending.

Because the sentence is talking about a specific addition and a specific report.

• viðbótin = the addition
• skýrsluna = the report

In Icelandic, each noun can be definite or indefinite on its own, depending on meaning.

For example:

• Viðbót við skýrsluna er stutt = An addition to the report is short
• Viðbótin við skýrslu er stutt = The addition to a report is short
• Viðbót við skýrslu er stutt = An addition to a report is short

So the definiteness of one noun does not automatically control the other.

Yes, but Viðbótin við skýrsluna er stutt is the most neutral, straightforward order.

Icelandic often follows a verb-second pattern in main clauses, so with the subject first, the finite verb er comes second:

• Viðbótin við skýrsluna er stutt

Other word orders are possible for emphasis or style, but they are less neutral. For a learner, this sentence is a good model to follow.

It is nominative singular, agreeing with the subject viðbótin.

With the verb vera = to be, predicate adjectives normally match the subject in gender, number, and case.

So here:

• viðbótin = feminine singular nominative
• stutt = feminine singular nominative form

That is why the adjective matches the subject even though it comes after the verb.