Biology Prefixes and Suffixes: epi-

Epidermis (skin surface). This is a colored scanning electron micrograph (SEM) of the surface of the skin of a 6-year-old. The outermost surface of the epidermis is composed of dead and dying skin cells from the underlying epidermis, which help to protect the delicate epidermal cells from the external environment.
Epidermis (skin surface). This is a colored scanning electron micrograph (SEM) of the surface of the skin of a 6-year-old. The outermost surface of the epidermis is composed of dead and dying skin cells from the underlying epidermis, which help to protect the delicate epidermal cells from the external environment.

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by Regina Bailey
Regina Bailey is a science writer and educator who has covered biology for ThoughtCo since 1997. Her writing is featured in Kaplan AP Biology 2016.
Updated July 14, 2018

The prefix (epi-) has several meanings including on, upon, above, upper, in addition to, near, besides, following, after, outermost, or prevalent.

Examples

Epiblast (epi-blast): the outermost layer of an embryo in an early stage of development, prior to the formation of germ layers. The epiblast becomes the ectoderm germ layer which forms skin and nervous tissue.

Epicardium (epi-cardium): the innermost layer of the pericardium (a fluid-filled sac that surrounds the heart) and the outermost layer of the heart wall.

Epicarp (epi-carp): the outermost layer of the walls of a ripened fruit; outer skin layer of fruit. It is also called the exocarp.

Epidemic (epi-demic): an outbreak of disease that is prevalent or widespread throughout a population.

Epiderm (epi-derm): the epidermis or outer skin layer.

Epididymis (epi-didymis): a convoluted tubular structure that is situated upon the upper surface of male gonads (testes). The epididymis receives and stores immature sperm and houses mature sperm.

Epidural (epi-dural): a directional term that means on or outside of the dura mater (outermost membrane covering the brain and spinal cord). It is also an anesthetic injection into the space between the spinal cord and dura mater.

Epifauna (epi-fauna): aquatic animal life, such as starfish or barnacles, that live on the bottom surface of a lake or sea.

Epigastric (epi-gastric): pertaining to the upper middle region of the abdomen. It also means lying on or over the stomach.

Epigene (epi-gene): occurring or originating at or near the earth's surface.

Epigeal (epi-geal): referring to an organism that lives or grows near or on the ground surface.

Epiglottis (epi-glottis): the thin flap of cartilage that covers the opening of the windpipe to prevent food from entering the opening during swallowing.

Epiphyte (epi-phyte): a plant that grows on the surface of another plant for support.

Episome (epi-some): DNA strand, typically in bacteria, that is either integrated in the host DNA or exists independently in the cytoplasm.

Epistasis (epi-stasis): describes the action of a gene upon another gene.

Epithelium (epi-thelium): animal tissue that covers the outside of the body and lines organs, vessels (blood and lymph), and cavities.

Epizoon (epi-zoon): an organism, such as a parasite, that lives on the body of another organism.