Let’s first look at the “technical” difference. I think the distinction is more obvious in the field of teaching or instructional design wherein an assessment helps gauge understanding and present opportunities to improve curriculum. An example of an assessment in this instance would be a pop quiz that doesn’t count towards a grade or survey to see what the class thinks about a project underway. An evaluation, on the other hand, would be a measure or judgement of “value,” more or less the “result” of the training or curriculum (such as a final exam).
In my own work, I tend to use these words interchangeably, but that’s probably because I don’t necessarily encourage the kind of things that would require differentiation. I could go into more detail but that’s probably content for a completely different question.
I learned an interesting concept about “definitions” a number of years ago from one of my undergraduate professors. Basically, “definitions gain power from those who give it to them.” I’m curious to hear what others think about this idea and if they support or oppose it.