A vitamin is an organic substance essential to metabolism, albeit in minute quantities. Vitamin are classed by their bodily retention.
Fat-soluble vitamins are stored in fat cells. These include vitamins A, D, E, and K.
Water-soluble vitamins are eliminated from the body the day they are digested. B and C are water-soluble.
The various vitamins were discovered by biochemists in the first decades of the 20th century. Some molecules originally thought to be vitamins turned out otherwise.
The vitamin formerly known as B4 is the nucleobase adenine. Erstwhile vitamin B11 was found to be a derivative of B9, and so scratched from the vitamin list.
Chronic vitamin deficiencies cause various diseases, every one gruesome in its own way.