Law and theory:
A law foretells what occurs whereas a theory proposes why. A theory may never turn into a law; however, the advancement of one regularly triggers advancements on the other.
A decent scientific law is a finely-tuned machine, achieving its assignment splendidly however ignorant of why it fills in just as it does. A decent scientific theory is a wounded, however unbowed, contender who fears defeat if unfit to adapt or over power to the next competitor.
Although unique, science needs both theories and laws to comprehend the entire picture. So, whenever somebody remarks that it's only a theory, challenge them to go nine rounds with the champ and check whether they can do any better.