The Perfect Progressive tense in Croatian grammar is used to describe an action that began in the past, is still ongoing, and is expected to continue in the future. It is formed by using the auxiliary verb “biti” (to be) in the present tense, followed by the present participle form of the main verb and the auxiliary verb “biti” in the present participle form.

For example, if we want to say “I have been reading this book for hours,” we would say “Ja sam čitao ovu knjigu već satima.” In this sentence, the auxiliary verb “sam” is in the present tense, the present participle form of “čitati” (to read) is “čitao,” and the auxiliary verb “biti” is also in the present participle form “sam.”

The Perfect Progressive tense is often used to talk about actions that are still happening at the moment of speaking or have recently finished. It adds a sense of duration and continuity to the action.