Luck or fortuity is good fortune which occurs beyond one's control, without regard to one's will, intention, or desired result. There are at least two senses people usually mean when they use the term, the prescriptive sense and the descriptive sense. In the prescriptive sense, luck is the supernatural and deterministic concept that there is a force which prescribes that certain events occur very much the way the laws of physics will prescribe that certain events occur. It is the prescriptive sense that people mean when they state that they "do not believe in luck." In the descriptive sense, luck is merely a name we give to events after they occur which we find to be fortuitous.
Luck as lack of control
Luck refers to that which happens to a person beyond that person's control. This view incorporates phenomena that are chance happenings, a person's place of birth for example, but where there is no uncertainty involved, or where the uncertainty is irrelevant. Within this framework one can differentiate between three different types of luck:
Constitutional luck, that is, luck with factors that cannot be changed. Place of birth and genetic constitution are typical examples.
Circumstantial luck—with factors that are haphazardly brought on. Accidents and epidemics are typical examples.
Ignorance luck, that is, luck with factors one does not know about. Examples can be identified only in hindsight.