Gratulasjonen er klar.

Because gratulasjonen is the definite singular form of the noun gratulasjon.

In Norwegian, the is usually added to the end of the noun instead of appearing as a separate word:

• gratulasjon = a congratulation / a congratulatory message
• gratulasjonen = the congratulation / the congratulatory message

So the ending -en is doing the job that the does in English.

Not usually in everyday speech.

If you want to say Congratulations! to someone, the normal Norwegian expression is:

• Gratulerer!

The noun gratulasjon is more likely to refer to a congratulatory message, greeting, speech, or formal congratulation. So in Gratulasjonen er klar, it sounds more like The congratulatory message is ready than the everyday English exclamation Congratulations!

Because the adjective has to agree with the noun.

Here, gratulasjonen is singular and treated as a common-gender noun in Bokmål, so the adjective is:

• klar = correct here

Compare:

• common gender singular: klar
• neuter singular: klart
• plural: klare

So:

• Gratulasjonen er klar = correct

If the noun were neuter, you would expect klart instead.

Here klar means ready or prepared.

So the sentence means something like:

• The congratulatory message is ready
• The congratulation is ready

In other contexts, klar can also mean clear, but that is not the most natural meaning here.

Because klar is being used predicatively, not directly in front of the noun.

In Gratulasjonen er klar, the structure is:

• gratulasjonen = subject
• er = verb
• klar = adjective after the verb

After er, Norwegian normally uses the plain agreeing adjective form:

• Boka er klar
• Maten er klar
• Barna er klare

If the adjective came before the noun, the structure would be different:

• den klare gratulasjonen

So the sentence is correct as written.

It is grammatical, but it is somewhat context-dependent and a bit formal or unusual on its own.

It makes sense if you are talking about something specific like:

• a written congratulatory message
• a speech
• a card
• a prepared greeting

For example, someone might mean:

• The congratulatory message is ready to send
• The speech of congratulations is ready

In everyday Norwegian, people often use more specific nouns, such as hilsen, melding, kort, or just say Gratulerer!

This is the normal word order for a simple Norwegian statement:

• Subject + verb + complement

So:

• Gratulasjonen = subject
• er = verb
• klar = complement

It works much like English The congratulatory message is ready.

If another element came first, Norwegian would usually move the verb into second position:

• Nå er gratulasjonen klar. = Now the congratulatory message is ready.

That is a very common Norwegian pattern.

Er klar describes a state: it is ready.

• Gratulasjonen er klar. = The congratulatory message is ready.

Blir klar describes a change: it becomes ready / is getting ready.

• Gratulasjonen blir klar snart. = The congratulatory message will be ready soon.

So er tells you the thing is already in that state, while blir focuses on the transition into that state.