Diese Folge ist kurz.

Because Folge is a feminine singular noun, and here it is in the nominative case.

The demonstrative word dies- changes its ending to match the noun:

• dieser = masculine nominative
• diese = feminine nominative
• dieses = neuter nominative

So with die Folge (feminine), you need diese Folge.

It is in the nominative case because it is the subject of the sentence.

In Diese Folge ist kurz, the thing being described is diese Folge, so that is the subject. The verb ist agrees with it.

A simple way to see it:

• What is short?
• This episode is short.

That makes diese Folge the nominative subject.

Because diese Folge is singular.

• ist = is for one thing
• sind = are for more than one thing

So:

• Diese Folge ist kurz. = one episode
• Diese Folgen sind kurz. = more than one episode

Because kurz is being used as a predicate adjective after the verb sein.

In German, adjectives usually behave in two different ways:

1. Before a noun: they take endings

   • eine kurze Folge

2. After a linking verb like sein, werden, or bleiben: they do not take endings

   • Die Folge ist kurz.

So kurz stays in its basic form here.

This is normal German main-clause word order:

• Diese Folge = subject
• ist = verb
• kurz = adjective/complement

German main clauses usually put the finite verb in second position. Here the subject comes first, so the verb comes second:

• Diese Folge | ist | kurz.

That is the standard, neutral order.

Yes. That is also correct, but the meaning is slightly different.

• Diese Folge = this episode
  This points to a particular one, often with more emphasis.

• Die Folge = the episode
  This is more neutral and just refers to the episode.

So both are grammatical, but diese is more specifically demonstrative.

No. Folge has several meanings depending on context.

Common meanings include:

• episode of a show or series
• sequence
• consequence
• result

In this sentence, the context probably makes it mean episode, but learners should know it is a flexible word.

The plural would be:

• Diese Folgen sind kurz.

Changes:

• Folge → Folgen (plural)
• ist → sind (plural verb)

Notice that diese stays diese in the nominative plural.

Normally, no. In standard German, a singular countable noun like Folge usually needs a determiner or article.

So you would normally say:

• Die Folge ist kurz.
• Diese Folge ist kurz.
• Eine Folge ist kurz.

Saying just Folge ist kurz would sound incomplete in ordinary standard German.

A rough English-friendly guide is:

DEE-zuh FOL-guh ist koorts

A slightly more accurate breakdown:

• Diese ≈ DEE-zuh
• Folge ≈ FOL-guh
• ist ≈ ist
• kurz ≈ koorts

A few pronunciation notes:

• w is not involved here; German z sounds like ts
• kurz ends with a ts sound
• the g in Folge is pronounced as a hard g

Here, diese is being used as a determiner (often called a demonstrative determiner), because it comes directly before the noun Folge.

• diese Folge = determiner + noun

If it stood alone, it would be a pronoun:

• Diese ist kurz. = This one is short.

So in your sentence, it is not standing alone; it is modifying Folge.