Evolution is a Scientific Theory that explains the diverse speciation we see on our planet today. Or, more simply put, why there are so many different species of plants, animals, fungi, bacteria, protists, and archaea. Evolution has two main components - Selection (either Natural, Artificial, or Sexual) and Genetic Mutation - that cause changes in the inherited characteristics of biological populations over successive generations.
I'm trying to pin down a definition for Evolution, hopefully in plain English, and some questions have come to mind:
Is this a fool's errand?
It depends on how specific you want to be. For example, gravity is a Scientific Theory. You can say something as simple as "gravity explains the attraction of two or more objects with mass." Or, you could go much deeper by explaining how gravity fits into general relitivity and quantum mechanics. It's up to you. This might shed some light on the matter:
"Scientfic Theories describe the causal elements responsible for a particular natural phenomenon, and are used to explain and predict aspects of the physical universe or specific areas of inquiry (e.g. electricity, chemistry, astronomy). Scientists use theories as a foundation to gain further scientific knowledge, as well as to accomplish goals such as inventing technology or curing disease."
Has Evolution itself evolved?
If so how has the definition evolved?
When evolution was first purposed it was known that species passed on their traits and charachteristics to their offspring. But, at the time, no one knew exactly what the mechanisim was. It wasn't until much later when DNA was discovered that we began to understand exactly how genetic mutation works. But, from its inception, both components of evolution were there.
Is there current consensus between Evolutionists on a definition?
There is scientfic consensus on the theory of evolution among academics in the Life Sciences (developmental and molecular biology, ecology, embryology, ontogeny, osteology, paleontology, etc).
When you say "evolutionists" I assume you are simply refering to people who accept the theory of evolution. But this really conflates the issue because the theory of evolution is a scientific term with a precise and defenitive meaning. How the lay person chooses to describe it has no bearing on the theory at all.
It would be like asking "do "Cellulists" have a concensus on how to define cells?" Likewise, Cell Theory is a scientfic term with a precise meaning. How people who accept the existance of cells choose to define it has nothing to do with the actual science.
Are there different schools of thought and definitions?
Like any theory, if you get deep enough into it, you will eventually find a small enough point where scientfic concensus finally starts to diverge. Imagine you're trying to prove to me that Ford Mustangs exist. And I ask you for a definition of a Ford Mustang. You could give me a very broad answer like "it's a car" or you could go into great detail. Now imagine I took two experts on Ford Mustangs and they got into a super in depth conversation about the vehichal. One of thme was pretty sure the screw for the exhaust manifold was a flat head and the other thought it took a diamond head.
It's going to be at this sort of depth scientist have thier disagreements on evolution. It's a level so finite most of us would wonder why they even care in the first place.