Die Spielregel gilt für das Kartenspiel.

Because the gender of a German compound noun is determined by its last element.

• die Spielregel → the last part is Regel, and Regel is feminine, so the whole word is feminine.
• das Kartenspiel → the last part is Spiel, and Spiel is neuter, so the whole word is neuter.

This is a very useful rule for compound nouns in German.

German often builds long nouns by combining smaller nouns.

• Spielregel = Spiel
  • Regel → literally game rule
• Kartenspiel = Karten
  • Spiel → literally card game

A good way to understand German compounds is to read them from right to left:

• the last part gives the main category
• the earlier part(s) describe it

So:

• Spielregel = a kind of Regel
• Kartenspiel = a kind of Spiel

Gilt is the 3rd person singular present tense of gelten.

So:

• gelten = to be valid, to apply
• gilt = applies / is valid

In this sentence, Die Spielregel gilt für das Kartenspiel, gilt means something like:

• applies to
• is valid for

Because gelten für is a common German pattern meaning:

• to apply to
• to be valid for

So:

• Die Spielregel gilt für das Kartenspiel. = The rule applies to the card game.

You should learn gelten together with für, since they often go together in this meaning.

The preposition für always takes the accusative case.

So after für, you use an accusative form:

• für den (masculine)
• für die (feminine / plural)
• für das (neuter)

Here, Kartenspiel is neuter, so:

• nominative: das Kartenspiel
• accusative: das Kartenspiel

It looks the same in nominative and accusative because neuter singular das does not change here.

Because German main clauses usually follow the verb-second (V2) rule.

In a normal statement, the conjugated verb comes in the second position:

• Die Spielregel | gilt | für das Kartenspiel

This is standard German word order for a main clause.

German often uses an article where English may or may not use one.

Here die can be understood as a generic definite article, meaning something like:

• the rule
• or more generally a rule of the game / the game rule

German frequently uses the definite article when speaking about something in a general or class-based way.

It is singular.

• die Spielregel = the game rule
• die Spielregeln = the game rules

Even though die can also be the plural article, here you know it is singular because:

• the noun is Spielregel, not Spielregeln
• the verb is gilt (singular), not gelten (plural)

The plural would be:

• Die Spielregeln gelten für das Kartenspiel.

Changes:

• Spielregel → Spielregeln
• gilt → gelten

So:

• singular: Die Spielregel gilt ...
• plural: Die Spielregeln gelten ...

Usually das Kartenspiel means a card game.

In some contexts, German can also use Kartenspiel for a deck/pack of cards, but the meaning depends on context.

In this sentence, because of Spielregel (game rule), the meaning is clearly about the game, not the physical cards.

A simple pronunciation guide is:

• Die ≈ dee
• Spielregel ≈ shpeel-ray-gəl
• gilt ≈ gilt
• für ≈ a bit like fyoor, but with a front rounded vowel
• das Kartenspiel ≈ dahs kar-ten-shpeel

A rough full version:

dee shpeel-ray-gəl gilt fyur dahs kar-ten-shpeel

The hardest sound for many English speakers is ü in für. It is not the same as English oo.