Event

An event is something which happens or takes place. An event is brief, possibly extremely brief. Not like a process, which takes time. 

Alternate meaning: an important activity, an item in a program, or the program as a whole.

Culture
 A special occasion, such as a wedding or other party, is a social event.

 Science 
 In physics (and in some kinds of philosophy), an event occurs at a point in time which can be distinguished because the state of the world changed.  Something was different before and after the event. 
 In special relativity (and general relativity), an event is a point in the spacetime continuum, i.e. it has a position in space and time.
 In experimental particle physics, an event refers to a set of elementary particle interactions recorded in a brief span of time.
 In probability a possible outcome of an experiment is called an elementary event, while a set of those (a subset of all) is called simply an event.
 In palaeontology, one speaks of extinction events.

 Telecommunications 
 In information processing, an event is a change in the properties received by an observer after being transmitted from an object.
 In computer science, an event is a software message that indicates something has happened. See event-driven programming. A number of protocols, such as MIDI, are also event-based.