Ulykken er tragisk.

In Norwegian, the definite article is often attached to the end of the noun instead of standing as a separate word.

• ulykke = accident
• ulykken = the accident

So -en here is the definite ending, roughly equivalent to English the.

The dictionary form is ulykke, which means accident.

In this sentence, it appears in the definite singular form:

• ulykke = an accident / accident
• ulykken = the accident

Er is the present tense of å være, which means to be.

So:

• å være = to be
• er = is / am / are

In this sentence, er means is.

Because tragisk is being used as a predicate adjective, not directly before the noun.

Compare:

• den tragiske ulykken = the tragic accident
  Here the adjective comes before the noun, so it takes the form tragiske.

• ulykken er tragisk = the accident is tragic
  Here the adjective comes after er, so it stays tragisk.

This is a very common pattern in Norwegian: predicate adjectives usually do not show definiteness.

Predicate adjectives in Norwegian usually agree with the noun in gender and number.

Since ulykken is a singular common-gender noun, the adjective takes the basic form:

• common gender singular: tragisk
• neuter singular: tragisk or sometimes effectively the same in spelling for this type of adjective
• plural: tragiske

So tragisk is correct here.

A useful comparison:

• et problem er tragisk = a problem is tragic
• ulykken er tragisk = the accident is tragic
• ulykkene er tragiske = the accidents are tragic

Yes, in Bokmål, many feminine nouns can be treated either as feminine or as common gender/masculine-style in the definite singular.

So you may see:

• ulykken
• ulykka

Both can mean the accident in Bokmål.

The sentence you were given uses ulykken, which is very common and completely standard.

This sentence is standard Bokmål.

In Nynorsk, you would more typically see:

• Ulukka er tragisk.

So the main difference is the noun form:

• Bokmål: ulykken
• Nynorsk: ulukka

No, this is the basic Norwegian sentence pattern:

• subject + verb + adjective/complement

So:

• Ulykken = subject
• er = verb
• tragisk = complement

This matches English quite closely:

• The accident is tragic.

A rough English-friendly guide is:

• Ulykken ≈ oo-LIK-ken
• er ≈ a short air / ehr
• tragisk ≈ trah-GISSK

A few pronunciation notes:

• y in Norwegian is not the same as English u or y. It is a rounded front vowel that many English speakers need to practice.
• kk is pronounced as a clear double consonant, so the middle of ulykken is held a little more firmly.
• The g in tragisk is pronounced.

Yes, if the accident has already been mentioned.

• Ulykken er tragisk. = The accident is tragic.
• Den er tragisk. = It is tragic.

Norwegian often uses den for a previously mentioned noun like ulykken.

They are related, but they do not work the same way grammatically.

• Ulykken er tragisk = The accident is tragic
  This is a full sentence.

• Den tragiske ulykken = The tragic accident
  This is a noun phrase, not a full sentence by itself.

So the first one tells you something about the accident.
The second one just names or describes the accident.