assignment

noun
[C] a task or piece of work that sb is given to do, usually as part of their job or studies:
You will need to complete three written assignments per semester.
◆ She is in Greece on an assignment for one of the Sunday newspapers.
◆ one of our reporters on assignment in China
◆ I had set myself a tough assignment.
◆ a business / special assignment
[U] the act of giving sth to sb; the act of giving sb a particular task:
his assignment to other duties in the same company