Ladeporten er åpen.

Because Norwegian usually writes compound nouns as one word.

So if the noun is made from something like lade + port, they combine into ladeport.

This is very common in Norwegian:

• togstasjon = train station
• bildekk = car tire
• sommerferie = summer vacation

English often uses separate words where Norwegian prefers a compound.

The ending -en is the definite article attached to the noun. It works like the in English.

So:

• en ladeport = a/the charging port / barn door / gate depending on context
• ladeporten = the charging port / the barn door / the gate

In Norwegian, the definite article is often added to the end of the noun instead of being a separate word.

Because in Norwegian, a noun often shows definiteness by taking an ending.

Here, ladeporten already means the ladeport, so you do not need a separate the-word.

Compare:

• en port = a gate
• porten = the gate

A separate determiner is only used in certain structures, especially with adjectives:

• den åpne porten = the open gate

The word ladeport is common gender in Bokmål, so it takes en in the indefinite singular and -en in the definite singular:

• en ladeport
• ladeporten

In Norwegian compounds, the last part usually determines the gender. Since port is common gender, ladeport is common gender too.

Åpen is an adjective meaning open.
So er åpen describes the current state: the gate/port is open.

Åpnet is the past participle of å åpne and is used differently:

• Porten er åpnet = the gate has been opened / is opened

So the difference is roughly:

• er åpen = it is in an open state
• er åpnet = it has been opened

For a simple description of condition, er åpen is the normal choice.

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

This sentence is a basic subject + verb + description structure:

• Ladeporten = subject
• er = is
• åpen = open

So it works like:

• Døren er lukket = The door is closed
• Vinduet er stort = The window is big

Åpen is an adjective, and Norwegian adjectives often change form depending on gender and number.

Typical forms are:

• åpen for common gender singular: en åpen port
• åpent for neuter singular: et åpent vindu
• åpne for plural or definite forms: åpne porter, den åpne porten

In Ladeporten er åpen, the noun is singular common gender, so åpen is the correct form.

Yes, that is possible in many contexts.

• Ladeporten er åpen simply states the fact that it is open.
• Ladeporten står åpen can emphasize that it is standing open or has been left open.

This is a common nuance in Norwegian with doors, windows, gates, and similar things.

So:

• er åpen = neutral description
• står åpen = often a bit more vivid or situational

You usually make a yes/no question by putting the verb first:

• Er ladeporten åpen? = Is the gate/port open?

This is a very common Norwegian pattern:

• Han er hjemme. → Er han hjemme?
• Døren er låst. → Er døren låst?

The letter å is a separate letter in Norwegian, not just a with a mark.

It is usually pronounced somewhat like the vowel in English more or saw, though exact pronunciation depends on accent and dialect.

So åpen does not sound like English ay-pen. The first sound is a rounded å sound.

Also remember:

• å can be a letter
• å can also be the infinitive marker meaning to, but not here

In åpen, it is simply part of the word.

Yes. After er, adjectives come after the verb, just as in English:

• Porten er åpen
• Huset er gammelt
• Barna er glade

This is called predicative use of the adjective.

If the adjective comes before the noun, it is attributive:

• en åpen port

So both are normal, but the structure changes depending on the sentence.

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

Basic statement:

• Ladeporten er åpen

If you begin with another element, the verb still comes second:

• Nå er ladeporten åpen
• I dag er ladeporten åpen

So Norwegian word order is flexible, but not completely free. The finite verb usually stays in position two in main clauses.