This is the 6th most frequent Czech word.
do
"Do" in Czech means "to" or "into."
Here, 'do' signifies the act of placing something inside or into another object. It introduces the destination container, which is 'taška' – bag.
Dala knihu do tašky.
She put the book into the bag.
In this usage, 'do' expresses a time frame, effectively meaning 'by' or 'until' in English. It specifies the deadline, which is 'pátek' – Friday.
Práce musí být dokončena do pátku.
The work must be completed by Friday.
In this sentence, 'do' indicates direction or movement towards a specific place, which is 'škola' – school in this instance.