What is the purpose of a definiton for Unconventional Warfare?

I started to present “What is the Scope of Unconventional Warfare?” as the first question for discussion but while writing the introduction I discovered that a couple of more fundamental questions need to be answered first. They are:

1.        What is the purpose of the definition of UW and why do we even need to define it?

2.        What are the characteristics or criteria for a good definition?

3.        How can we test a definition to ensure it is rational, useful and pertinent to our stated purposes?