Ĉe la strando ni aŭdas la ondojn en la vespero.

At the beach we hear the waves in the evening.

Breakdown of Ĉe la strando ni aŭdas la ondojn en la vespero.

• la: the
• en: in
• ni: we
• ĉe: at

Questions & Answers about Ĉe la strando ni aŭdas la ondojn en la vespero.

Why does ondojn end with -jn?

Because it has two endings at once:

• -j = plural
• -n = direct object

The basic word is ondo = wave.
So:

• ondo = a wave
• ondoj = waves
• ondon = a wave, as a direct object
• ondojn = waves, as a direct object

In this sentence, the waves are the thing that we hear, so they take the accusative -n.

Why is there no -n on vespero in en la vespero?

Here en la vespero is a prepositional phrase, and the preposition en already shows the relationship: in / during the evening.

Normally, nouns after prepositions do not take -n unless there is a special reason, such as showing movement toward something in certain expressions.

So:

• en la vespero = in the evening
• la vesperon would be a direct object, which is not the role here

What does ĉe mean here?

Ĉe usually means something like at, by, near, or in the area of.

So ĉe la strando means at the beach or by the beach.

It does not always mean physically on top of something. It often gives a general location.