[ lahy-kuhn ]
/ 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.

Origin of lichen

1595–1605; <Latin līchēn<Greek leichḗn


li·chen·i·za·tion, nounli·chen·like, adjectiveun·li·chened, adjective


lichen , liken. Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Example sentences from the Web for lichen

British Dictionary definitions for lichen

/ (ˈlaɪkən, ˈlɪtʃən) /


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

Derived forms of lichen

lichened, adjectivelichen-like, adjectivelichenoid, adjectivelichenous or lichenose, adjective

Word Origin for lichen

C17: via Latin from Greek leikhēn, from leikhein to lick
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for lichen

[ līkən ]


Any of various skin diseases characterized by patchy eruptions of small, firm papules.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for lichen

[ līkən ]

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.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.