The Korean national flag is called Taegukki. The meaning of Korean National Flag is very philosophical. The origin comes from the old oriental philosophy called the theory of Um-Yang, in Chinese pronunciation Yin-Yang. Yin means dark and cold, while Yang means bright and hot. The idea of Yin-Yang is supposed to be originated from the old Korean philosophy of Samshin meaning three gods. A very old book called Chuyok or Iching in Chinese, which was written by (a) Chinese several thousands years ago, claims all objects and events in the world are expressed by the movement of yin and yang. For example, the moon is yin while the sun is yang; the earth is yin and the heaven is yang; a woman is yin and a man is yang; the night is yin and the day is yang; the winter is yin and the summer is yang, etc. Yin and yang are relative. Therefore, A can be yin with respect to B while A can also be yang with respect to C. For instance, the spring is yin w.r.t. the summer and it is at the same time yang w.r.t. the winter. Yin and yang are opposite and struggle each other while they cooperate in harmony. The harmonious state of the movement of yin and yang is called Taeguki, or Taikukkki, Taichi in Chinese, which is also the name of the Korean national flag, i.e. Taegukki. Ki means a flag. (See the similarity between the concept of Yin-Yang-Taichi and the dialectics of thesis-antithesis-synthesis.) The upper half circle, red, of Taeguk means yang and the lower half circle, blue, means yin. They stand for the state of harmony of yin and yang.