This is the 276th most frequent Finnish word.
joku
"Joku" means "someone" or "somebody" in English.
Here, 'jonkun' appears again in the genitive case, showcasing its possessive usage with a definite group.
Tapasin kaupungilla jonkun ystävistäni.
I met one of my friends in the city.
The word 'joku' is used here as an indefinite pronoun to refer to an unspecified person.
Joku soitti ovikelloa.
Someone rang the doorbell.
The word 'jonkun' is a genitive form of 'joku', used to indicate possession in this context.