Tunnelen er lang.

Because tunnelen is the definite form: the tunnel.

In Norwegian, the definite article is usually attached to the end of the noun:

• en tunnel = a tunnel
• tunnelen = the tunnel

So Norwegian often expresses the with a suffix instead of a separate word.

Norwegian usually adds definiteness directly to the noun.

So instead of:

• English: the tunnel

you normally get:

• Norwegian: tunnelen

This is one of the first big differences English speakers notice. The noun itself changes form to show the.

Yes. Er is the present-tense form of å være (to be), and here it means is.

Examples:

• Tunnelen er lang. = The tunnel is long.
• Huset er stort. = The house is big.

Unlike English, Norwegian verbs do not change depending on the subject:

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

So er is used with all persons in the present tense.

Because lang is being used predicatively—that means it comes after er and describes the subject.

Compare:

• Tunnelen er lang. = The tunnel is long.
• den lange tunnelen = the long tunnel

When an adjective comes after a verb like er, it usually appears in its basic agreement form:

• en tunnel er lang
• et hus er langt
• husene er lange

So here tunnel is a common-gender singular noun, which matches lang.

You learn it together with its article:

• en tunnel

That tells you it is a common gender noun in Bokmål.

This matters because adjectives and definite forms depend on gender:

• en lang tunnel
• tunnelen er lang

If it were neuter, you would expect forms like:

• et ...
• adjective often with -t in some positions, for example langt

Not with tunnelen, because tunnel is not neuter.

You would use langt with a neuter noun:

• Et løp er langt. = A race is long.

But with en tunnel / tunnelen, the correct form is:

• Tunnelen er lang.

No, this is a very basic Norwegian sentence pattern:

• Subject + verb + adjective

So:

• Tunnelen = subject
• er = verb
• lang = adjective

It works very much like English:

• The tunnel is long.

Then Norwegian uses a different structure:

• en lang tunnel = a long tunnel
• den lange tunnelen = the long tunnel

Notice two things:

1. The adjective changes:
   • lang → lange in the definite phrase
2. Norwegian often uses both:
   • a separate definite marker den
   • and the definite ending on the noun -en

So:

• tunnelen er lang = the tunnel is long
• den lange tunnelen = the long tunnel

A rough pronunciation guide is:

• Tunnelen ≈ TUNN-eh-len
• er ≈ ær or a light ehr
• lang ≈ lahng

A very approximate full version could be:

• TUNN-eh-len ær lahng

A few notes:

• u in tunnel is not like English you
• ng in lang is like the ng in sing
• Norwegian pronunciation varies somewhat by dialect

The basic forms are:

• en tunnel = a tunnel
• tunnelen = the tunnel
• tunneler = tunnels
• tunnelene = the tunnels

This is useful because you may later see:

• Tunnelene er lange. = The tunnels are long.

Notice how the adjective changes to lange in the plural.

Usually lang means long, especially in a physical sense, as in this sentence.

But like English, it can also be used more broadly in other contexts, depending on the noun:

• en lang dag = a long day
• en lang film = a long film

Still, in Tunnelen er lang, the most natural meaning is physical length.