Definitions for "Simple pendulum"
a hypothetical pendulum suspended by a weightless frictionless thread of constant length
a linear system only when the oscillations of the pendulum are constrained to be quite small (as they are in introductory physics classes)
a mechanical system that displays oscillatory motion
a point (small) mass suspended by a light (of negligible mass) string
a mass swinging on the end of a massless string under the influence of gravity.
a simple machine based on the effect of gravity