This is the 66th most frequent Romanian word.
unul
"Unul" in Romanian means "one" (as a pronoun or numeral).
The word 'unul' is used here as a pronoun meaning 'one (of)' to refer to a singular item or person from a larger group.
Unul din prietenii mei este arhitect.
One of my friends is an architect.
The word 'unul' is part of the phrase 'unul câte unul,' which means 'one by one,' a set expression in Romanian.
Unul câte unul, participanții au început să părăsească sala.
One by one, the participants started to leave the hall.
The word 'unul' functions as a pronoun substituting a previously mentioned or implied noun.