This is the 76th most frequent Turkish word.
biri
"Someone" or "one."
Here, 'biri' is used as an indefinite pronoun meaning 'someone', referring to an unspecified person.
Biri kapıyı çaldı.
Someone knocked on the door.
In this sentence, 'biri' means 'one', referring to a single item within a group.
Bu koltuklardan biri senin olabilir.
One of these chairs can be yours.
Here, 'biri' is utilized to refer to a singular, specific but unidentified person within a specified group.