How can you tell the difference between a chemist and a plumber? Ask them to pronounce "unionized."
It's funny because: A more labor-conscious plumber would pronounce the word as "yoon-yun-ized." A chemist would probably say "un-eye-on-ized."
It's on this list because: What other joke can simultaneously address the removal of charged particles from an atom as well as the organization of workers trying to achieve shared goals?