维生素；维他命(vitamin)
饮食中所需的小量有机化合物，可以维持身体的正常代谢功能。当人们了解到维生素并非全是胺（亦即不是全部含氮）时，1911年所创的vitamine一词即变为vitamin。许多维生素充当（或转变为）辅。它们不提供能量，也不并入组织里。水溶性维生素（维生素B复合体、维生素C）很快被身体排出。脂溶性维生素（维生素A、维生素D、维生素E、维生素K）需要胆盐才能被吸收，并储存在体内。已知许多维生素的正常功能，而缺乏特定维生素会导致疾病（包括脚气病、神经管缺陷、恶性贫血、佝偻病、坏血病）。维生素（特别是脂溶性维生素）过量也是危险的：维生素A太多导致肝脏受损，这种後果在有β－胡萝卜素时看不见，因为身体会将β－胡萝卜素转化为维生素A。已知几种维生素会支援免疫系统。大部分的维生素在均衡饮食中供给充足，但需求量较高的人可能需要补充。
English version：
vitamin
Organic compound required in small amounts in the diet to maintain normal metabolic functions. The term “vitamine” (1911) was changed to “vitamin” when it was realized that not all vitamins were amines (i.e., not all contained nitrogen). Many vitamins act as or are converted to coenzymes. They neither provide energy nor are incorporated into tissues. Water-soluble vitamins (vitamin B complex, vitamin C) are excreted quickly. Fat-soluble vitamins (vitamin A, vitamin D, vitamin E, and vitamin K) require bile salts for absorption and are stored in the body. The normal functions of many vitamins are known. Deficiency of specific vitamins can lead to diseases (including beriberi, neural tube defect, pernicious anemia, rickets, and scurvy). Excess amounts, especially of fat-soluble vitamins, can also be dangerous: too much vitamin A causes liver damage, an effect not seen with beta-carotene, which the body converts into vitamin A. Several vitamins are now known to support the immune system. Most vitamins are adequately supplied by a balanced diet, but people with higher requirements may need supplements.