Biology Prefixes and Suffixes: ex- or exo-

Close-Up Of Cicada Exoskeleton On Wood. Credit: Kaori Kurita/EyeEm/Getty Images

Biology Prefixes and Suffixes: ex- or exo-


The prefix (ex- or exo-) means out of, away from, outer, external, outside, or exterior.


Excoriation (ex-coriation) - a scratch or abrasion on the outer layer or surface of the skin.

Exergonic (ex-ergonic) - a biochemical process that involves the release of energy.

Exfoliation (ex-foliation) - the shedding of cells or scales from the outer tissue surface.

Exobiology (exo-biology) - the study of and search for life in the universe outside of Earth.

Exocarp (exo-carp) - the outer most layer of the walls of a ripened fruit; outer skin layer of fruit.

Exocrine (exo-crine) - refers to the secretion of a substance externally. It also refers to glands that secrete hormones through ducts that lead to epithelium rather than directly into the blood. Examples include sweat and salivary glands.

Exocytosis (exo-cytosis) - process by which substances are excreted from a cell. The substance is contained within a vesicle that fuses with the outerĀ cell membrane. The substance is thereby exported to the exterior of the cell.

Exoderm (exo-derm) - outer germ layer of a developing embryo that forms skin and nervous tissue.

Exogamy (exo-gamy) - the union of gametes from organisms that are not closely related, as in cross pollination. It also means to marry outside of ones culture or social unit.

Exogen (exo-gen) - a flowering plant that grows by increasing layers on its exterior tissue.

Exons (ex-on) - sections of DNA that code for the messenger RNA molecule produced during protein synthesis.

Exonuclease (exo-nuclease) - an enzyme that digests DNA and RNA by cutting out a single nucleotide at a time from the end of the molecules.

Exophoria (exo-phoria) - a tendency for one or both eyes to move outward.

Exophthalmos (ex-ophthalmos) - abnormal outward bulging of the eyeball.

Exoskeleton (exo-skeleton) - hard outer structure that provides support or protection for an organism; outer shell.

Exotoxin (exo-toxin) - a poisonous substance produced by some bacteria that is excreted into their surrounding environment. Exotoxins cause serious damage to host cells.