Something that, if prevented, removed or eliminated, will prevent the occurrence of the event in question, and or, if permitted, introduced or maintained, will be followed by the event in question. A necessary cause is a a cause that must exist if a given event is to occur, but may not itself result in the event. A sufficient cause is one which is inevitably followed by a given event or the existence of a given thing.
Something that brings about a particular condition, result, or effect.