The reasons for this are many. There are scientific terms and definitions, there are method terms and definitions, and there are words that are very general and encompass a broad spectrum of possibilities.
Early on, I made myself a glossary of dog training terms that are the meanings as I understand them to be per my prior experience and training. It does not mean someone else's other definition is wrong! It is just nice to understand what each other's definition is, and what your own personal definition is. Sometimes two people are saying the same thing, but arguing about it due to the misunderstanding of what each person is actually trying to say. I give to you my personal glossary of dog training terms: