is: any oscillatory system that exhibits oscillations which can be described by an equation of the form
with solutions of the form 
is exemplified: by a mechanical oscillator exhibiting simple harmonic motion.
is also exemplified: by an electrical circuit in which an inductor of inductance 
is connected across a charged capacitor of capacitance 
with the result that the charge 
on the capacitor satisfies the differential equation
where 
and where the charge then is given at time 
by 
with 
and 
arbitrary constants.
Copyright 1997, The Open University