Ah, that sentence makes sense, I just couldn't work out the syntax ("specificity" just didn't seem to fit in). My problem, not yours :)

I didn't explain it clearly at all, but the point I was trying to make was that there is quite a bit of "technical" language/jargon which acts as a stopsign (and/or induces blankness). "Prior" doesn't really fit into this category, but "probability distribution" does, and the Wikipedia article (probably) doesn't really help people from your target audience.

I would suggest removing the term completely (or maybe having the technical term in a parenthetical statement) e.g.

The prior is not a number, but a measurement of the probability of each of a spectrum of possible alternatives