Slangen er lang.

Because Norwegian usually puts the definite article onto the end of the noun.

• slange = the basic noun form
• slangen = the snake

So the ending -en works like English the here.

In Norwegian, the definite article is very often a suffix, not a separate word in front.

Compare:

• en slange = a snake
• slangen = the snake

That is one of the big differences from English.

The dictionary form is slange.

Norwegian dictionaries usually list nouns in the indefinite singular form, so if you see a word like slangen, it is useful to recognize that the ending -en has been added to the base noun slange.

Er is the present tense of å være = to be.

It can mean am, is, or are in English, depending on the subject:

• jeg er = I am
• du er = you are
• han er = he is
• de er = they are

Unlike English, Norwegian does not change the form of the verb for different persons in the present tense.

Because slange is a masculine singular noun, and the adjective has to match that.

For this adjective:

• masculine/feminine singular: lang
• neuter singular: langt
• plural: lange

So:

• slangen er lang = correct
• huset er langt = with a neuter noun
• slangene er lange = with a plural noun

Because lang is being used as a predicate adjective here: it comes after er and describes the subject.

In Norwegian, predicate adjectives do not take a special definite form. They mainly agree in gender and number, not definiteness.

Compare:

• den lange slangen = the long snake
  Here lange comes before the noun, so it is attributive.

• slangen er lang = the snake is long
  Here lang comes after er, so it is predicative.

That is why lang is correct here.

Yes, in this simple sentence it is very similar.

Structure:

• Slangen = subject
• er = verb
• lang = adjective/complement

So it works like English The snake is long.

You would say En slange er lang.

Compare:

• en slange = a snake
• slangen = the snake

So the main change is whether the noun is indefinite or definite.

A rough guide is:

• slangen ≈ SLAH-ngen
• er ≈ a short air-like sound
• lang ≈ lahng

A few useful points:

• ng sounds like the ng in sing
• the a in lang is broader than the a in cat
• the final g in lang is not pronounced like a hard English g

Exact pronunciation varies by dialect, but this will get you close.

No, not the way they are in German.

Common nouns are normally written with a lowercase letter unless they begin a sentence. So Slangen has a capital S here only because it is the first word of the sentence. In the middle of a sentence, it would be slangen.