This is the 431st most frequent Catalan word.
comença
"Comença" means "begins" or "starts" in English.
Here, 'comença' means 'begins' or 'starts' and denotes the action of starting to perform an activity, specifically reading a book.
Ell comença a llegir un llibre nou.
He begins to read a new book.
In this question, 'comença' indicates the start time of an event, making it an inquiry about the event's starting point.
Quan comença la festa?
When does the party start?
Here, 'comença' describes the habitual or standard beginning point of a sequence, specifically the start of the week with Monday.