The moment of time at which a specified change of state occurs; usually marks the completion of an asynchronous input/output operation.

An incident of probable tectonic significance, but whose full implications are unknown.

A specified accomplishment in a program at a particular time; appears as a node in a graphic representation of an endeavor with a specific objective (project).

A point in space- time.

A mathematical model of the result of a conceptual experiment; this model is a measurable subset of a probability space.