This is the 361st most frequent Croatian word.
počeo
"Počeo" means "started" or "began" in English.
In this sentence, 'počeo' is used to indicate the beginning of an action performed by a male subject, specifically the action of working.
Počeo je raditi jučer.
He started working yesterday.
Here, 'počeo' is used in the first person singular form to express the initiation of the action of reading.
Počeo sam čitati novu knjigu.
I started reading a new book.
The word 'počeo' denotes the beginning of the boy's crying as a reaction to falling.