Reiseruten er lang.

Because Norwegian usually writes compound nouns as one word.

So:

• reise = travel
• rute = route / itinerary

Together, reiserute means travel route or itinerary.

Then -n / -en is added to make it definite:

• en reiserute = a travel route / an itinerary
• reiseruten = the travel route / the itinerary

This is very normal in Norwegian. Where English often uses two words, Norwegian often prefers one compound word.

Reiseruten is a singular definite noun.

A useful breakdown is:

• reiserute = itinerary / travel route
• reiseruten = the itinerary / the travel route

The noun reiserute is a common gender noun, so its forms are typically:

• en reiserute = an itinerary
• reiseruten = the itinerary
• reiseruter = itineraries
• reiserutene = the itineraries

So in the sentence, reiseruten is the subject.

In Norwegian, the is often expressed by adding an ending to the noun instead of using a separate word like English does.

So:

• en reiserute = an itinerary
• reiseruten = the itinerary

The definite meaning is built into the noun itself.

This is one of the biggest differences from English. English uses a separate article (the), but Norwegian very often uses a suffix on the noun.

Because lang is a predicate adjective here, and it agrees with the noun in number and gender.

Here, reiseruten is:

• singular
• common gender

So the adjective stays in its basic form:

• Reiseruten er lang. = The itinerary is long.

Compare:

• Et brev er langt. = A letter is long.
  
  • langt is used with a neuter singular noun.
• Reiserutene er lange. = The itineraries are long.
  
  • lange is used with plural.

So lange would be wrong here because the subject is singular, not plural.

Because lang is not part of a noun phrase here. It is a predicate adjective after the verb er.

Structure:

• Reiseruten = subject
• er = is
• lang = adjective describing the subject

This works much like English:

• The itinerary is long.

You would not say the itinerary is a long in English, and similarly you do not put an article before lang in Norwegian.

Er is the present tense of å være, which means to be.

So:

• jeg er = I am
• du er = you are
• han/hun er = he/she is
• vi er = we are

In Reiseruten er lang, er links the subject to a description:

• Reiseruten = the itinerary
• er = is
• lang = long

So it works exactly like is in English.

Usually, lang means long in a general sense, but the exact nuance depends on context.

With reiserute, it most naturally suggests that the route or itinerary is long/extended, which could imply:

• a long distance
• a lot of stages or stops
• a lengthy overall journey

If the surrounding context is about kilometers, it may feel more like long in distance.
If the context is about the whole trip plan, it may feel more like lengthy/extended.

So the sentence is grammatically simple, but the exact shade of meaning comes from context.

No, this is the normal basic word order for a simple Norwegian statement:

• Subject + verb + complement

So:

• Reiseruten = subject
• er = verb
• lang = complement

This is very similar to English:

• The itinerary is long.

If you turned it into a yes/no question, Norwegian would usually invert the subject and verb:

• Er reiseruten lang? = Is the itinerary long?

The adjective would change to match.

With a common gender singular noun:

• Reiseruten er lang.

With a neuter singular noun:

• Kartet er langt. = The map is long.

With a plural noun:

• Reiserutene er lange. = The itineraries are long.

So the adjective forms are:

• lang = common gender singular
• langt = neuter singular
• lange = plural

This is a very common adjective pattern in Norwegian.

A rough guide for an English speaker is:

• Reiseruten ≈ RYE-seh-roo-ten
• er ≈ a quick air or ehr
• lang ≈ lahng

A few notes:

• The r in Norwegian may sound different depending on dialect.
• ei/rei in reise is often like the English eye sound.
• u in ruten is usually a rounded vowel, not exactly like English oo, though roo is a decent approximation for beginners.
• lang has the ng sound as in English sing.

Pronunciation varies by dialect, but that approximation will usually be understood.

Yes, in many varieties of Norwegian, especially Bokmål usage influenced by everyday speech, reiseruta can also occur.

You may see both:

• reiseruten
• reiseruta

They both mean the itinerary / the travel route.

Why both forms exist:

• Many feminine nouns in Bokmål can take either:
  • a feminine definite ending -a
  • or a common-gender-style definite ending -en

Whether reiserute is treated as feminine or common gender can vary by style and speaker.

So both can be acceptable, depending on the variety of Bokmål and the writer’s preference.