Pendulum: A mass that swings back and forth on a rigid rod or string. An ideal pendulum has all of its mass centered in a single point and the string is massless and frictionless. The word pendulum comes from the Latin for hanging or swinging.
Oscillating: Moving back and forth in a repetitive motion.
Kinetic Energy: The energy of motion defined as KE= ½mv2
Gravitational Potential Energy: The stored mechanical energy. ΔPE = mgΔh
Total Mechanical Energy: Kinetic energy plus the potential energy.
Isochronous: A constant time period.
Period: The amount of time it takes to complete one cycle, revolution, or swing.
Frequency: How often a cycle is completed. The inverse of the period.
Functional dependence: How does a quantity depend on another quantity, such as position as a function of time x(t)