Joseph Wilson 
Chapter 11 - Definitions
The word I will be using is contactor.

Write a parenthetical definition.
The lighting circuit is controlled with a photocell, time clock and contactor (a device to break and re-establish the circuit) combination.
Write a sentence definition.
A contactor is a device used to repeatedly break and re-establish the electric circuit under normal conditions.
Write a short expanded definition of that term. I used negation instead of other forms of expanded definitions.
A contactor is a device used to repeatedly break and re-establish the electric circuit under normal conditions. It is used for many reasons like being used for higher voltages and loads, being used for three phase systems, and being used for overload protection and arc suppression. It is not the same as relay which is used for single phase systems, lower voltages and loads, and where the need for safety systems are minimal.