-derm Also -dermatous.
[Greek derma, skin, hide.]
Several terms refer to an embryo, such as blastoderm (Greek blastos, germ or sprout), a blastula (an embryo at an early stage of development) that has the form of a disc of cells on top of the yolk; and the set ectoderm (Greek ektos, outside), mesoderm (Greek mesos, middle), and endoderm (Greek endon, within), respectively the outermost, middle, and inner layers of cells of an embryo in early development. In botany, the periderm (Greek peri, about, around) is the corky outer layer of a plant stem formed in secondary thickening or as a response to injury or infection. A pachyderm (Greek pakhus, thick) is a very large mammal with thick skin, especially an elephant, rhinoceros, or hippopotamus.
Other examples are the names of existing or fossil species of animal, such as echinoderm (Greek ekhinos, hedgehog, sea urchin), a member of a group of marine invertebrates which includes starfishes, sea urchins, and sea cucumbers; placoderm (Greek plax, plak-, flat plate), a fossil fish of the Devonian period.
Linked adjectives are formed in -dermatous, though these are relatively rare: echinodermatous, pachydermatous.