Der Reifen des Fahrrads ist platt.

Breakdown of Der Reifen des Fahrrads ist platt.

sein
to be
das Fahrrad
the bicycle
der Reifen
the tire

Questions & Answers about Der Reifen des Fahrrads ist platt.

Why is there an –s at the end of Fahrrads in des Fahrrads?

In German the genitive singular of most masculine and neuter nouns takes an –s or –es.

  • das Fahrrad (neuter) → des Fahrrads (genitive)
  • You’ll often see just -s on polysyllabic nouns (like Fahrrad).
  • On some monosyllabic nouns (e.g. Name) you’ll get -es (→ des Namens).
When should I use the genitive case instead of von + dative (e.g. des Fahrrads vs. vom Fahrrad)?
  • Genitive (des Fahrrads) is more formal and bookish; it directly marks possession.
  • von + dative (vom Fahrrad) is very common in spoken, everyday German.
    Example:
    Der Reifen des Fahrrads ist platt. (written, formal)
    Der Reifen vom Fahrrad ist platt. (colloquial)
Why is the verb ist in second position (“Der Reifen des Fahrrads ist platt”)?

German main clauses follow the V2 rule: the finite verb must be the second element.
1) First element (subject/expression): Der Reifen des Fahrrads
2) Second element (verb): ist
3) Rest of the sentence: platt

If you front something else, the verb still stays second:
Platt ist der Reifen des Fahrrads.

Why isn’t platt inflected with an ending (e.g. platter, plattes)?

Because platt here is a predicative adjective (after a form of sein). Predicative adjectives never take endings.

  • Ich bin müde. (not müder)
  • Der Ball ist rund. (not runder)

Only attributive adjectives (those placed before a noun) require endings:

  • ein platter Reifen
  • der runde Tisch
How do I know Reifen is singular and not plural here?

German often has identical singular and plural forms. You rely on the article:

  • der Reifen = singular nominative
  • die Reifen = plural nominative

Since we see der , it tells us it’s singular.

Could I say Der Fahrradreifen ist platt instead of Der Reifen des Fahrrads ist platt?

Yes. German loves compound nouns.

  • Fahrrad + ReifenFahrradreifen
  • So Der Fahrradreifen ist platt is perfectly natural and more concise.
Why do some people write des Fahrrades instead of des Fahrrads?
In older or very formal texts you might find -es on some neuter nouns. Modern standard German generally prefers -s, but -es is still understood and not “wrong” in a literary/archaic style.
What other ways can I say Der Reifen des Fahrrads ist platt in German?

You have a few colloquial options:

  • Ich habe einen Platten. (I’ve got a flat.)
  • Der Reifen hat eine Panne. (The tire has a breakdown.)
  • Die Luft ist raus. (The air’s gone.)
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How do German cases work?
German has four grammatical cases: nominative (subject), accusative (direct object), dative (indirect object), and genitive (possession). The case determines the form of articles and adjectives. For example, "the dog" is "der Hund" as a subject but "den Hund" as a direct object.

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