Vitamin A is a general term for a class of fat-soluble vitamins, primarily including retinol, retinal, retinoic acid, and its precursor carotenoids (such as beta-carotene). It is an essential nutrient for the human body and cannot be synthesized naturally; it must be obtained through food or supplements.

Vitamin A's primary functions in the body include maintaining normal vision, promoting epithelial growth and repair, supporting immune function, and participating in reproductive and developmental processes. Vitamin A deficiency can lead to night blindness, dry skin, and weakened immunity.