This is the 35th most frequent Spanish word.
uno
"Uno" means "one" in English.
The word "uno" is used here as a pronoun meaning "one" referring to people in general.
Uno siempre debe esforzarse por aprender.
One should always strive to learn.
In this sentence, "uno" represents a noun, implying an item or object.
Quiero comprar uno, pero no tengo suficiente dinero.
I want to buy one, but I don't have enough money.
Here, "uno" stands for an individual, indicating a person who might arrive.