Feieluken er viktig for atkomsten.

Feieluken is a compound noun:

• feie = to sweep
• luke = hatch, flap, small door, opening

So feieluke is a kind of cleaning hatch / sweep hatch, often something related to chimney sweeping, soot removal, or maintenance access.

Norwegian uses compound nouns very freely, so long words like this are very common.

Because it is in the definite singular form.

The basic form is:

• en feieluke = a cleaning hatch

The definite form is:

• feieluken = the cleaning hatch

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

The noun is common gender:

• en feieluke
• feieluken

In Norwegian compounds, the last part usually decides the gender of the whole word. Here the last part is luke, which is a common-gender noun, so feieluke is common gender too.

Here, luke means a hatch, panel, small access door, or opening with a cover.

It does not mean a regular door like dør. It usually refers to something smaller or more technical. You see it in words like:

• takluke = roof hatch
• inspeksjonsluke = inspection hatch

So in feieluke, the idea is a hatch used for cleaning or sweeping access.

Atkomst means access, approach, or way of getting to something, especially physical access.

• en atkomst = an access / an approach
• atkomsten = the access

It is definite here because the sentence is talking about a specific access situation or a known access route in context. Norwegian often uses the definite form in places where English might simply say access without the.

So for atkomsten is literally for the access, but in natural English that may simply be for access depending on the context.

Because viktig for is a very common Norwegian pattern meaning important for.

Examples:

• viktig for sikkerheten = important for safety
• viktig for helsa = important for health
• viktig for atkomsten = important for access

So for shows what something is important for, affects, or matters to.

No, it is completely normal.

The structure is:

• Feieluken = subject
• er = verb
• viktig = adjective/predicative
• for atkomsten = prepositional phrase

So this is a standard Norwegian main clause:

Subject + verb + complement

Nothing unusual is happening with the word order here.

Because viktig is being used predicatively, after the verb er.

Compare:

• Feieluken er viktig. = The cleaning hatch is important.
• en viktig feieluke = an important cleaning hatch

When the adjective comes after er, you do not use an article with it. This is the same basic idea as in English:

• The hatch is important
• not The hatch is an important unless a noun follows

Not especially. It sounds somewhat formal or technical, and it is common in contexts like:

• building descriptions
• property information
• safety regulations
• construction or maintenance texts

In everyday speech, people might use other expressions depending on the situation, such as:

• inngang = entrance
• vei inn = way in
• komme til = get to / reach

So atkomst is perfectly correct, but it has a slightly technical feel.

Sometimes English uses access for both ideas, but Norwegian often separates them.

• atkomst = physical access, approach, way to get to a place
• tilgang = access in the sense of availability, permission, having access to something

So if the sentence is about physically reaching something, atkomst is the better word.

For example:

• atkomst til bygget = physical access to the building
• tilgang til systemet = access to the system

That is why atkomsten makes good sense here.