Yin Yang

Y is for Yin Yang

The yin yang symbol is ancient, steeped in symbolism and meaning.  Many 

philosophers have attempted to explain the universe in terms of this symbol.

Below is an excerpt from the poem "Identity of Relative and Absolute", written by

 Zen Master Shih-t'ou Hsi-ch'ien  (700-790 CE)

Picture courtesy of Wikipedia

 當明中有暗    In the light there is darkness,
勿以暗相遇    but don't take it as darkness;
當暗中有明    In the dark there is light,
勿以明相睹    but don't see it as light.
明暗各相對    Light and dark oppose one another
比如前後歩    like the front and back foot in walking.
萬物自有功    Each of the myriad things has its merit,
當言用及處    expressed according to function and place.
事存函蓋合    Phenomena exist; box and lid fit;
理應箭鋒拄       principle responds; arrow points meet.

 

Yangin' around

"Y" is for Yin-Yang 
 

The yin-yang symbol represents the ancient Chinese Taoist idea that there are two energies - the yin energy and the yang energy - that created the universe, and oppose each other to keep the universe in balance.  If you go too far along one, it becomes the other.  A great example of this is temperature.  If you put your hand in a bucket of ice water at first it feels really cold.  But if you leave it in there longer, you will feel a burning sensation - just like heat. 

Yin-yang is the unifying principle in Traditional Chinese Medicine (including proper diet and exercise).

You can find a very interesting pictorial explanation of how this symbol was developed here.

And here's what wikipedia has to say on the subject.
  
There's much symbolism within the symbol itself, and there's a myriad of interpretations. Here's a few of the ones I like: