This is the 51st most frequent Slovenian word.
kaj
"What"
'Kaj' is used as a questioning pronoun to ask for information about an action or activity.
Kaj delaš?
What are you doing?
'Kaj' acts as a relative pronoun introducing a dependent question about food.
Povej mi, kaj si jedel za kosilo.
Tell me what you ate for lunch.
'Kaj' is again a relative pronoun, introducing a dependent clause that specifies the unknown event.