Commentary: endeavor, endeavour, try - earnest and conscientious activity intended to do or accomplish something (count noun)
He made an effort to cover all of the reading material for the class.
She gave a good effort.
The book was her finest effort.
WordNet 2.0 Sense Numbers: 1, 3, 4
Commentary: elbow grease, travail, sweat - use of physical or mental energy; hard work (mass noun)
He got an A for effort.
They managed only with great effort.
WordNet 2.0 Sense Numbers: 2