Questions & Answers about Ich sehe ein Zeichen an der Wand.
Why is the article before Zeichen ein and not einen?
Because Zeichen is a neuter noun. The indefinite article for neuter in both nominative and accusative is ein. The form einen would be used only for masculine nouns in the accusative.
Why is an der Wand in the dative case, and could it ever be accusative?
The preposition an is a two-way (Wechsel-) preposition. It takes dative when indicating location (answering wo?, “where?”) and accusative when indicating direction or movement (answering wohin?, “where to?”). Here you’re stating where you see the sign (it’s on the wall), so it’s dative: an der Wand. If you were moving something onto the wall, you’d use accusative: an die Wand.
Why does the verb sehen require ein Zeichen in the accusative?
sehen is a transitive verb, which means it needs a direct object. In German, all direct objects take the accusative case. Hence ein Zeichen is accusative as the object of sehen.
Could you use a definite article instead of ein, for example das Zeichen? What’s the difference?