The epidermis is the outermost of the three layers that make up the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss. The epidermis is composed of multiple layers of flattened cells that overlie a base layer (stratum basale) composed of columnar cells arranged perpendicularly.
The word epidermis is derived through Latin from Ancient Greek epidermis, itself from Ancient Greek epi, meaning ‘over, upon’ and from Ancient Greek derma, meaning ‘skin’. Something related to or part of the epidermis is termed epidermal.