Ideen er glimrende.

Because ideen is the definite singular form: the idea.

• idé = idea
• ideen = the idea

In Norwegian, the definite article is usually added to the end of the noun rather than written as a separate word.

So:

• en idé = an idea
• ideen = the idea

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

Here, the noun is idé, and when it becomes definite, it takes the ending -en:

• idé → ideen

This is very common in Norwegian:

• en bil → bilen
• en stol → stolen
• en idé → ideen

Because Norwegian usually puts the at the end of the noun instead of using a separate article before it.

English:

• the idea

Norwegian:

• ideen

This is one of the biggest structural differences from English. In a simple sentence like this, ideen already includes the meaning of the idea.

Er is the present tense of å være (to be).

So it works just like is in English:

• Ideen er glimrende.
• The idea is excellent.

Some other forms of å være are:

• er = is / am / are
• var = was / were
• vært = been

This is the normal word order for a basic statement in Norwegian:

subject + verb + complement

So here:

• Ideen = subject
• er = verb
• glimrende = adjective/complement

This is very similar to English:

• The idea is excellent.

Glimrende is an adjective. It describes the noun ideen.

In this sentence, it comes after er, so it is being used as a predicative adjective:

• Ideen er glimrende.

Compare that with an adjective before a noun:

• en glimrende idé = an excellent idea

So the same adjective can appear:

• before a noun: en glimrende idé
• after a form of to be: ideen er glimrende

Because glimrende is one of the adjectives that usually stays the same.

Many Norwegian adjectives change depending on gender/number:

• en stor bil
• et stort hus
• store biler

But adjectives ending in -ende often do not change:

• en glimrende idé
• et glimrende forslag
• glimrende ideer
• ideen er glimrende

So glimrende is conveniently stable.

Yes. Glimrende is much stronger than plain good.

Depending on context, it can mean things like:

• excellent
• brilliant
• splendid

So Ideen er glimrende sounds clearly positive and enthusiastic, not just mildly approving.

Yes, absolutely.

That sentence means This is an excellent idea, while Ideen er glimrende means The idea is excellent.

The difference is mainly:

• ideen = a specific idea already known in the conversation
• en glimrende idé = an indefinite noun phrase, often when introducing or evaluating it

So both are natural, but they are built differently.

A rough guide is:

• ideen ≈ ee-DEH-en

The stress is on the second syllable.

A more detailed approximation:

• i- like ee
• -de- with a clear stressed vowel
• -en as a short final ending

If you have seen the base form idé, notice that when the ending is added, the word becomes ideen.

A rough English-friendly guide is:

• glimrende ≈ GLIM-ren-deh

The stress is usually at the beginning: GLIM-.

Do not try to pronounce it exactly like an English word; just aim for a short, clear Norwegian rhythm.

Yes. The usual indefinite form is:

• en idé

Then the definite form is:

• ideen

So the full pattern is:

• en idé = an idea
• ideen = the idea

It is neutral and natural. It works well in both speech and writing.

The adjective glimrende is fairly strong and positive, but not unnatural or overly formal. It is a perfectly normal way to praise an idea.