This is the 73rd most frequent Czech word.
nás
"Us" (objective form).
In this sentence, 'nás' functions as a direct object of the verb 'těšit', meaning 'please' or 'make happy', referring to 'us'.
Těší nás tvoje návštěva.
We are pleased with your visit.
Here, 'nás' is used as a direct object of the verb 'vybrat', meaning 'choose', again representing 'us'.
Šéf vybral nás na tuto důležitou úlohu.
The boss chose us for this important task.
In this example, 'nás' functions as the object of the preposition 'bez', meaning 'without', referring to 'us'.