Questions & Answers about Die Wellen am Ufer waren sehr hoch.
Why is it am Ufer instead of an dem Ufer?
am is the standard contraction of the preposition an (at/on) and the dative article dem. In German, these are almost always merged unless you want to emphasize a specific shore. Since das Ufer is a neuter noun, the dative article is dem, creating am.
Why do we use the dative case here instead of the accusative?
The preposition an is a two-way preposition. Because the waves are at a fixed location (at the shore) rather than moving toward a new destination, we use the dative case. If the sentence used a directional preposition like entlang (along), which you are learning in this lesson, we would use the accusative case to show a path of movement.
What is the singular form of die Wellen?
Why use waren instead of sind ... gewesen?
waren is the simple past tense of sein (to be) for plural subjects, translating directly to 'were'. Although spoken German usually prefers the two-part spoken past (Perfekt) for most actions, the simple past forms war (was) and waren (were) are the standard choice for 'to be' even in casual everyday speech.