The ancient Chinese concept of opposing characteristics or traits in nature is described with the terms yang and yin. The concept relates directly to dominance and subordinance, advancing and receding. Yang represents dominant, advancing, assertive traits. Yin represents subordinate, receding, receptive traits. More specifically, to the Chinese, yin means gentleness and softness—the grace of the willow tree, and the delicacy of the moon. Yang means strength and vigor— the sturdiness of the pine tree, and the force of the sun.