It is at present generally believed that there was only 疾 but not 病 in the disease-related oracle bone inscriptions. This implies that there was no distinction between the two characters in the late Shang Dynasty, and that their concepts were not thoroughly understood in the Yin and Shang dynasties either. It was not until the middle of the Warring States period that the word 病 began to gradually replace the word 疾. In the early years of the Western Han Dynasty, the word 病 had a slight advantage. Since the Eastern Han Dynasty, the meanings of 疾病 (disease) and 生病 (to catch a disease) have been basically used instead of 疾. However, from the oracle bone inscriptions, there are about two kinds of characters: 、 and . These different types of hieroglyphs indicate different situations. The word 疾 in oracle bone inscriptions has not merely different glyphs but different concepts of human diseases as well. Therefore, this paper intends to trace back to the concept and usage of 疾 and 病 in the late Shang Dynasty from the shape of the word 疾 in oracle bone inscriptions, and to the evolution of the meanings of 疾 and 病 in ancient literature.