Semantics I would say Tim. We can all look elsewhere and not see what was right in front of us. The Aikido word for yin yang would be harmony would it not? (in plain english) A much talked about thing by Ueshiba.
No, the Japanese words for yin/yang are the two words in Japanese explained already in this thread. Yin and yang are two separate things and as I'm sure you know within medicine, the natural world, and yes in martial arts different phenomenon are ascribed as either yin or yang influenced...while harmony may be a desired state of balance in which a given thing is neither too yin nor too yang, how you think that the concepts and application can simply be reduced to "harmony" is beyond me.