Both of them belong to Dioscorea, Dioscoreaceae, especially the yam produced in Xinxiang, Henan, so they are called yam (Dioscorea opposita). Efficacy: benefiting qi and nourishing yin, strengthening spleen, lung and kidney. Used for: 1. Spleen deficiency and weak qi, eating less loose stool or diarrhea. 2. Kidney deficiency nocturnal emission, frequent urination, and excessive female leucorrhea. 3. Asthma and cough due to lung deficiency. 4. Treat diabetes. Usage and dosage: decoction 10-30G, large dosage 60-250G. Tonifying yin should be used raw, strengthening spleen and stopping diarrhea should be fried yellow.