What is the definition of epicenter and focus?

Answer 1

epicenter is the point on earths surface directly above an earthquakes starting point,or focus

focus is the point along a fault at which the first motion of an earthquake occurs

Answer 2

The epicenter is the point on the Earth's surface directly above the focus of an earthquake, where the seismic waves are most strongly felt. The focus, or hypocenter, is the actual location underground where the earthquake originates.