  This chapter provides an overview of the possibilities for transient and
variable-source astrophysics with the Square Kilometre Array. While subsequent
chapters focus on the astrophysics of individual events, we focus on the
broader picture, and how to maximise the science coming from the telescope. The
SKA as currently designed will be a fantastic and ground-breaking facility for
radio transient studies, but the scientifc yield will be dramatically increased
by the addition of (i) near-real-time commensal searches of data streams for
events, and (ii) on occasion, rapid robotic response to Target-of-Opprtunity
style triggers.
