Definition of tae kwon do for English Language Learners. : a style of fighting that originated in Korea and that uses kicks and punches but no weapons. Britannica.com: Encyclopedia article about tae kwon do.
It is also used in the baking process as a leavening agent; yeast releasing gas into their environment results in the spongy-like texture of breads and cakes. Because of its role in fermentation, humans have known about and used Saccharomyces cerevisiae for a long time.
Yeast is a leavening agent. Yeast releases CO2 as a waste product. Bread dough has protein structures called Gluten. The CO2 from the yeast gets trapped in pockets between the gluten strands, thus causing the dough to rise. When the bread bakes, the yeast continues to reproduce and create CO2 gas. The yeast eventually dies when the temperature of the dough gets hot enough. Without yeast, bread would be flat and tough.