This is the 10th most frequent Serbian word.
што
"Што" in Serbian means "what," "why," or "that," depending on the context.
The word 'што' here introduces a relative clause, similar to 'which' or 'that' in English.
Шта је то што држиш у руци?
What is that which you are holding in your hand?
The word 'што' is used here colloquially as 'why' to ask a question about the reason.
Што не идеш са нама у биоскоп?
Why don't you come with us to the cinema?
In this sentence, 'што' connects an explanation or commentary to the main clause, translated as 'which' in English.