The phrase "a lengthy assignment" is correct and usable in written English.
You can use it to describe an assignment that requires a significant amount of time or effort to complete.
Example: "The professor assigned a lengthy assignment that will take several weeks to finish."
Alternatives: "a long assignment" or "an extensive assignment".
It is tradition at the end of an Agent's lengthy assignment to the First Family to get a personal send off from the President and First Lady.
"Completing a lengthy research assignment was a challenge for me," Aimee recalls, "and I felt that rather than her thinking I was not engaged in my work, that I would share what was happening to me". For Aimee, opening up that dialogue made her job situation easier.
only technically, as they ride out unguaranteed contracts on the bench or on lengthy assignment in the D-League before drifting to the N.B.A.'s fringes.
Try chewing on a piece of gum or squeezing a stress ball as you work on particularly lengthy assignments.
Teachers who give lengthy assignments or report cheating are made to feel like Torquemada.
His first priority was always his family, which is why he refrained from accepting lengthy assignments abroad, even when, in the 1950s and 60s, his work was being shown widely in Life and Vogue.
This was a lengthy and complex assignment worth a substantial portion of the course grade.
And what if Hamilton, who probably will have a lengthy minor league rehabilitation assignment before joining the Angels, struggles to retain his form?
The campaign is the first work for AARP from the organization's new brand advertising agency, Grey New York, which was selected to handle the assignment after a lengthy review.
The task of replacing Jeter for now falls to Eduardo Nunez, who had spent several days preparing to move to third in the seemingly likely event that Alex Rodriguez, who is nearing the end of a rehabilitation assignment, receives a lengthy suspension by Major League Baseball.
