[lahy-kuh n] /ˈlaɪ kən/
any complex organism of the group Lichenes, composed of a fungus in symbiotic union with an alga and having a greenish, gray, yellow, brown, or blackish thallus that grows in leaflike, crustlike, or branching forms on rocks, trees, etc.
Pathology. any of various eruptive skin diseases.
verb (used with object)
to cover with or as if with lichens.
an organism that is formed by the symbiotic association of a fungus and an alga or cyanobacterium and occurs as crusty patches or bushy growths on tree trunks, bare ground, etc. Lichens are now classified as a phylum of fungi (Mycophycophyta)
(pathol) any of various eruptive disorders of the skin
c.1600, from Latin lichen, from Greek leichen, originally “what eats around itself,” probably from leichein “to lick” (see lick). Originally used of liverwort; the modern sense first recorded 1715. Related: Lichenaceous.
lichen li·chen (lī’kən)
Any of various skin diseases characterized by patchy eruptions of small, firm papules.
The mutualistic symbiotic association of a fungus with an alga or a cyanobacterium, or both. The fungal component of a lichen absorbs water and nutrients from the surroundings and provides a suitable environment for the alga or cyanobacterium. These live protected among the dense fungal hyphae and produce carbohydrates for the fungus by photosynthesis. Owing to this partnership, lichens can thrive in harsh environments such as mountaintops and polar regions. The more familiar lichens grow slowly as crusty patches, but lichens are found in a variety of forms, such as the tall, plantlike reindeer moss. The association between the different organisms in a lichen is so close that lichens are routinely referred to as a single organism, and scientists classify lichens using the name of the fungal component.
- Lichen myxedematosus
lichen myxedematosus lichen myx·e·de·ma·to·sus (mĭk’sĭ-dē’mə-tō’səs) n. A skin condition characterized by the widespread eruption of papules or plaques of mucinous edema caused by the deposition of acid mucopolysaccharides in the skin. Also called papular mucinosis.
- Lichen nitidus
lichen nitidus lichen nit·i·dus (nĭt’ĭ-dəs) n. A skin condition characterized by minute, asymptomatic, whitish or pinkish, flat-topped skin papules that may occur in conjunction with lichen planus.
lichenoid li·chen·oid (lī’kə-noid’) adj. Resembling lichen.
- Lichenoid dermatosis
lichenoid dermatosis n. A chronic skin eruption characterized by hardening and thickening of the skin with the accentuation of normal skin markings.