Thomson identified at least three distinct meanings associated with evolution in contemporary biology:
change over time,
common ancestry, and
the natural mechanisms that produce change in organisms.
This essay will further refine these distinctions and present six distinct meanings. In so doing, we want to help science educators distinguish well-established from less well-established senses of the term evolution.
We also want to help teachers avoid false controversies over senses of the term that enjoy wide scientific confirmation and support and to help them explain the real controversies that remain over more theoretically contentious propositions.