1. energy: mental or physical energy that is exerted in order to achieve a purpose I wish they'd put a little more effort into it.
2. activity directed toward particular end: activities undertaken by a group of people in order to achieve a particular goal or overcome a particular difficulty the peacekeeping effort
3. attempt: an attempt to do something, especially one that involves a considerable amount of exertion, work, or determination He made an effort to improve things.
4. result of attempt: the result of a sincere attempt to do or make something It's not bad for a first effort.
5. physics applied force: the force input force applied to a simple machine that produces an effect output force on the load
[15th century. < French< Old French esforcier "exert power" < Latin fortis "strong"]
