Feildiagnosen viser at tilleggsarbeid er nødvendig.

Norwegian very often joins nouns into a single compound word.

So feildiagnosen is built from:

• feil = error, wrong, fault
• diagnose = diagnosis
• the definite ending = the

The base noun is en feildiagnose in the indefinite singular, and feildiagnosen in the definite singular.

A useful detail: many common-gender nouns ending in -e form the definite singular with -n, so:

• en diagnose → diagnosen
• en feildiagnose → feildiagnosen

So the whole word means the feildiagnose in whatever sense the context gives.

Yes.

• å vise = to show
• viser = shows / is showing

In Norwegian, verbs do not change according to the subject the way they do in English. So you get:

• jeg viser
• du viser
• han/hun viser
• vi viser

The form stays the same.

At introduces a subordinate clause and corresponds to English that.

So:

• viser at ... = shows that ...

In this sentence, the clause after at is:

• tilleggsarbeid er nødvendig

That whole clause is the content of what is being shown.

English often drops that, but in Norwegian it is usually safest and most natural to keep at here.

Usually, no, not if you simply mean shows that.

There is an important difference:

• viser at = shows that, demonstrates that
• viser til = refers to, points to, cites

So in this sentence, viser at is the normal choice if the meaning is that something demonstrates a conclusion.

If you said viser til at, the meaning would shift toward refers to the fact that or points out that, which is not exactly the same.

Because Norwegian normally writes compound nouns as one word.

Tilleggsarbeid is made from:

• tillegg = addition, extra amount, supplement
• arbeid = work

Together, tilleggsarbeid means something like additional work or extra work.

This is very typical Norwegian spelling. Where English often writes two words, Norwegian often uses one compound word.

Because tilleggsarbeid is being used in a general, mass-noun sense, like English additional work.

So the sentence is talking about extra work as a concept, not about one clearly counted item.

That is why you get:

• tilleggsarbeid er nødvendig

rather than something with en or et.

This is similar to how English says work is necessary, not a work is necessary, when work means labor in general.

Here nødvendig is an adjective used after er, so it is a predicate adjective:

• er nødvendig = is necessary

A point that often confuses learners: adjectives ending in -ig usually do not add -t in the neuter singular.

So you get:

• et nødvendig tiltak
• arbeidet er nødvendig

not nødvendigt.

The plural/definite form is different:

• nødvendige tiltak

This is normal subordinate-clause word order.

After at, Norwegian uses:

• subject + verb + complement

So:

• tilleggsarbeid = subject
• er = verb
• nødvendig = complement

That gives:

• at tilleggsarbeid er nødvendig

This is different from the special verb-second pattern that Norwegian uses in main clauses. After a subordinating word like at, you do not use main-clause inversion.

It is an adjective.

More specifically, it is a predicate adjective, because it comes after the verb er and describes the subject tilleggsarbeid.

So the structure is:

• tilleggsarbeid = subject
• er = linking verb
• nødvendig = adjective describing the subject

This is the same basic pattern as:

• Huset er stort
• Boken er interessant
• Tilleggsarbeid er nødvendig