This is the 42nd most frequent Italian word.
uno
"Uno" means "one" in English.
Here, 'uno' is used as a pronoun meaning 'one' to indicate a singular element out of a group.
Uno dei miei passatempi preferiti è leggere.
One of my favorite hobbies is reading.
In this context, 'uno' functions as an indefinite article equivalent to 'a' before singular masculine nouns starting with a z or s+consonant.
Ho comprato uno zaino nuovo per il viaggio.
I bought a new backpack for the trip.
Here, 'uno' is used as a pronoun meaning 'one,' highlighting a specific quantity in a question.