This is the 925th most frequent Serbian word.
ко
"Who"
The word 'ко' is used as an interrogative pronoun asking about the identity of a person.
Ко је ово на слици?
Who is this in the picture?
The word 'ко' serves as a relative pronoun introducing the subordinate clause.
Желим да знам ко се пријавио на курс.
I want to know who applied to the course.
Here, 'ко' functions as a relative pronoun identifying the person who performs a specific action.