A while back I talked to a sailmaker about this, and he said the term gennaker can be ambiguous, so if somebody orders a gennaker, he has to have them clarify exactly what type of sail they are talking about. I think the term "spinnaker" is universally understood, which is why I suggested using that word in the rules. Not everybody is going to go down and check the definitions if they think they already know what a word means. It would be unfortunate if somebody ordered the wrong type of sail for this class just because of a simple word misunderstanding.