This is the 275th most frequent Czech word.
ulici
"Ulici" means "street" (in the accusative or locative case) in English.
Here, 'ulici' is the locative case of 'ulice', used to indicate location.
Viděl jsem ho na ulici.
I saw him on the street.
In this sentence, 'ulici' is in the locative case, used again to express being at a location.
Procházel se po ulici.
He was walking along the street.
Here, 'ulici' is in the accusative case, functioning as a direct object to denote the destination in motion.