Hyphens, En Dashes, Em Dashes

Q. Is it prework or pre-work (for work that is to be done before a meeting)?

A. Prework is a pretty silly concept, if you think about it. I mean, is it work or not? It would be like preeating. How about calling it “preparation”?

[This answer relies on the 17th edition of CMOS (2017) unless otherwise noted.]