Applausen fra publikum var stor efter forestillingen.

The -en makes the noun definite singular: applausen = the applause.

The basic noun is applaus = applause.
Because applaus is a common-gender noun in Danish, its definite singular form is made with -en:

• en applaus = an applause / applause
• applausen = the applause

In this sentence, Danish uses the definite form because it refers to the specific applause after the performance.

Both can exist, but they are used a little differently.

• fra publikum often means from the audience in a more general or collective sense
• fra publikummet points more explicitly to the audience as a definite group

In many contexts, especially with nouns like publikum, Danish often uses the bare noun after a preposition in a way that sounds natural and idiomatic.

So applausen fra publikum is a very natural way to say the applause from the audience.

Publikum is a noun meaning audience. It is a collective noun, referring to a group of people as one unit.

A learner may expect something more like the people in the audience, but Danish often just uses publikum.

It is also one of those nouns that often appears without an article in places where English would strongly prefer the.

Because stor agrees with applausen, and applaus is a common-gender singular noun.

With predicate adjectives after verbs like være (to be), Danish still shows agreement:

• common gender singular: stor
• neuter singular: stort
• plural / definite plural contexts: store

So:

• Applausen var stor = correct
• Applausen var stort = incorrect

Compare:

• Huset var stort = The house was big
• Applausen var stor = The applause was great/strong

Yes. In Danish, stor is commonly used in a broad sense like great, strong, considerable, or impressive.

So applausen var stor does not mean the applause was physically large. It means something like:

• the applause was great
• the applause was strong
• there was a lot of applause

This is normal Danish usage.

Because here stor is a predicate adjective, not an adjective directly modifying the noun inside the noun phrase.

Compare the two structures:

• den store applaus = the great/loud applause
  
  • adjective is inside the noun phrase
• applausen var stor = the applause was great/loud
  
  • adjective comes after var and describes the subject

English works the same way:

• the loud applause
• the applause was loud

Var is the past tense of være (to be).

So:

• er = is / are
• var = was / were

In this sentence, var means was because the subject is singular:

• Applausen ... var stor = The applause ... was great

Forestillingen means the performance or the show.

The base noun is forestilling.
Its definite singular form is forestillingen.

That definite form is used because the sentence refers to a specific performance, presumably the one that has just been mentioned or is obvious from context.

• en forestilling = a performance
• forestillingen = the performance

It is a time expression meaning after the performance.

More literally:

• efter = after
• forestillingen = the performance

So this phrase tells us when the applause was great.

The sentence structure is:

• Applausen fra publikum = subject
• var = verb
• stor = predicate adjective
• efter forestillingen = time phrase

Yes. Danish is a V2 language, which means the finite verb normally stays in the second position in main clauses.

So you can say:

• Applausen fra publikum var stor efter forestillingen.
• Efter forestillingen var applausen fra publikum stor.

Both are grammatical. The second version gives a little more focus to the time phrase after the performance.

Because this is a straightforward main clause with the subject first, which often looks quite similar in Danish and English.

The basic pattern is:

• Subject + verb + complement + adverbial

Here:

• Applausen fra publikum = subject
• var = verb
• stor = complement
• efter forestillingen = adverbial

Danish can look very English-like in simple statements, although its word order becomes more obviously different when something other than the subject is placed first.

Usually it behaves like an uncountable noun, much like applause in English.

So in a sentence like this, it refers to applause in general, not to one separate clap or one separate instance.

That is why applausen var stor is best understood as the applause was great/strong, not as a countable item.

Yes, it is grammatical and natural. A Danish speaker would understand it immediately.

Depending on style, some speakers might also say something like:

• Bifaldet fra publikum var stort efter forestillingen.
• Der var stor applaus fra publikum efter forestillingen.

But the original sentence is perfectly good Danish.