Your definitions are essentially correct. I offer the following suggestions for clarification:
Voltage: The amount of energy pushing electrons around a circuit. Voltage is also called potential difference, and is likened to pressure.
Capacitance: The ability to allow current flow in proportion to the rate of voltage change. Capacitors charge and discharge, allowing maximal current when voltage changes are highest. Capacitance is expressed as Farads. It is the ability to store a charge.
Current: No suggestions.
Period of a wave: The time between two equivalent points on the wave (for example crests or troughs), usually expressed in seconds.
Frequency: Number of wave cycles per second, expressed as Hertz.
Wave length: No suggestions.