This is the 521st most frequent Russian word.
задач
The word "задач" is the genitive plural form of "задача," meaning "tasks" or "problems."
Here, 'задач' is used in the plural genitive case to express the quantity of tasks.
У нас много задач, которые надо решить.
We have many tasks that need to be solved.
Here, 'задач' appears in the plural genitive case embedded within a possessive ('of the project').
Определение задач проекта займёт некоторое время.
Defining the project's tasks will take some time.
In this sentence, 'задачами' is used in the plural instrumental case to indicate means or tools of dealing.