What does COM mean in an electrical wiring diagram?

Answer 1

Meaning of the term "COM" in Electrical Wiring DiagramsUsually, that is an abbreviation for the word, "Common"which means the return side of all, or almost all, components, which are connected to this common point or series of points all connected together.

Also, almost always this point or series of interconnected common points is the "Negative, or Ground," connection in DC [Direct Current] circuit applications, and the "Neutral" connection in AC [Alternating Current] circuit applications.