Breakdown of Stolpernd tritt er auf ein Spielzeug.
ein
a, an (eine)
er
he
auf
on / to (down/up to a level)
das Spielzeug
the toy
Questions & Answers about Stolpernd tritt er auf ein Spielzeug.
How is stolpernd formed, and why doesn't it have an ending like an adjective?
Stolpernd is the Present Participle (Partizip I) of the verb stolpern (to stumble). You form it simply by adding -d to the infinitive. Since it is used here as an adverb describing how he steps—rather than as an adjective describing a noun—it does not take any grammatical endings.
Why is the word order tritt er instead of er tritt?
In German, the conjugated verb must be in the second position of a main clause. Because the sentence starts with the adverb stolpernd in position one, the verb tritt must come immediately after it in position two, pushing the subject er to the third position.
Why does the sentence use auf ein Spielzeug (accusative) instead of auf einem Spielzeug (dative)?
The preposition auf is a two-way preposition. It takes the accusative case when it describes a movement or direction towards a destination, answering the question 'where to?'. Here, he is moving his foot onto the toy, so the neuter noun das Spielzeug takes the accusative form ein Spielzeug.
The infinitive of the verb is treten. Why is the form here tritt?