Trigger

A Trigger is a basic process which either forms the preconditions for a subsequent consequent event or process or is the precipitating cause of the event. For example, some presently unknown set of conditions is believe to be the trigger for the commencement of an ice age. Or in the case of a super saturated solution addition of a seed crystal will trigger the precipitation of the dissolved material. The example given in chaos theory of a butterfly causing a great weather disturbance is an example of a trigger.

Manufactured devices such as guns may incorporate trigger mechanisms.