Formkurven viser terskelfarten.

It follows a very basic subject–verb–object pattern:

• Formkurven = the subject
• viser = the verb
• terskelfarten = the object

So structurally it works like English X shows Y.

Because Norwegian usually puts definiteness at the end of the noun instead of using a separate article.

• formkurve = a form curve

• formkurven = the form curve

• terskelfart = a threshold pace/speed
• terskelfarten = the threshold pace/speed

So the English word the is built into the noun here.

The ending -en is the normal definite singular ending for many common-gender nouns in Bokmål.

Here that gives:

• en formkurve → formkurven
• en terskelfart → terskelfarten

So -en does not mean the same thing as English -en in words like wooden. It is a grammar ending marking the.

Because Norwegian writes compounds as one word much more often than English does.

• form + kurve → formkurve
• terskel + fart → terskelfart

This is very common in Norwegian. A native English speaker may want to split them up, but in Norwegian that would usually be incorrect.

Viser is the present tense of å vise, meaning to show.

Examples:

• jeg viser = I show / I am showing
• du viser = you show
• den viser = it shows

Norwegian verbs do not change for person the way English does. The same viser is used with all subjects in the present tense.

Yes. Norwegian simple present often covers both:

• shows
• is showing

Which English version sounds best depends on context. Norwegian does not need a special progressive form here.

Yes. It is a compound noun:

• terskel = threshold
• fart = speed / pace

So terskelfart literally means something like threshold pace or threshold speed. In sports or training contexts, this is fairly natural technical vocabulary.

Sometimes, yes.

The noun kurve can often be treated as a feminine noun in Bokmål, so you may see:

• en formkurve → formkurven
• ei formkurve → formkurva

Both can be acceptable depending on style, dialect, and how much feminine marking the writer uses.
In this sentence, formkurven is completely standard.

In a normal declarative sentence like this, Norwegian usually shows that through word order.

• Formkurven viser terskelfarten = The form curve shows the threshold pace

The noun before the verb is normally the subject, and the noun after the verb is normally the object.

If you swapped them:

• Terskelfarten viser formkurven

that would mean The threshold pace shows the form curve, which is a different meaning.

Yes, but Norwegian keeps the verb in second position in main clauses.

For example, if you move another element to the front, the verb still stays second:

• På grafen viser formkurven terskelfarten.
  = On the graph, the form curve shows the threshold pace.

And in a yes/no question:

• Viser formkurven terskelfarten?
  = Does the form curve show the threshold pace?

So the basic sentence is simple, but Norwegian word order follows clear rules.

No. In this sentence, -en marks definiteness, not case.

Modern Norwegian has very little case marking on nouns. So:

• formkurven means the form curve
• terskelfarten means the threshold pace

The sentence relies mainly on word order, not case endings, to show who does what.