li·​chen | \ˈlī-kən, British also ˈli-chən\

Definition of lichen 

1 : any of numerous complex plantlike organisms made up of an alga or a cyanobacterium and a fungus growing in symbiotic association on a solid surface (such as on a rock or the bark of trees)

Note: The main body of the lichen, known as the thallus, is formed by fungal filaments which surround the photosynthetic algal or cyanobacterial cells. The lichen is usually described as having a leaflike (foliose), crusty (crustose), or branching shrub-like (fruticose) form. Lichens often play an important part in the weathering of rocks and include some that are sources of natural dyes.

2 : any of several skin diseases characterized by the eruptions of flat papules

Illustration of lichen

Illustration of lichen

lichen 2

Keep scrolling for more

Other Words from lichen

lichened \ ˈlī-​kənd , British also  ˈli-​chənd \ adjective
lichenous \ ˈlī-​kə-​nəs , British also  ˈli-​chə-​ \ adjective

Examples of lichen in a Sentence

Recent Examples on the Web

BETA GLUCANS Long-chain sugar molecules found in the cell walls of bacteria, fungi, yeasts, algae, lichens, and grains, such as oats and barley. Allure, "The Skin-Care Glossary: A Comprehensive Guide to Everything You Need to Know," 17 Aug. 2018 Their three variations, known as ecomorphs, include a brown spider that lives among rocks, a gold spider that lives under leaves, and a white spider that lives on lichen. Sophie Weiner, Popular Mechanics, "Hawaiian Spiders on Different Islands Evolved the Same Traits," 9 Mar. 2018 Most likely the gray growth is from lichens formed from a combination of harmless fungus and algae. Tom Maccubbin,, "Prune blueberry bushes after fruiting," 23 June 2018 If lichens need control, a copper-containing fungicide specific for figs or a general fruit tree use can be applied to reduce their growth following label instructions. Tom Maccubbin,, "Caterpillar invasion isn't end for healthy tree," 14 July 2018 The artistic installation features 100 pounds of moss, lichens, other botanical specimens and string models of Einstein-Rosen bridges, or wormholes. Christine Clarridge, The Seattle Times, "Explore Seattle’s map of ‘high weirdness’: Ghost canoe, rumored troll, Hell Mouth — and more," 28 June 2018 Considerable growth of lichens usually indicates the plants are not vigorous enough to maintain good foliage cover. Tom Maccubbin,, "Prune blueberry bushes after fruiting," 23 June 2018 Dr Bohannon set up a sting operation by writing versions of a paper falsely claiming that a molecule found in lichens inhibits cancer. The Economist, "Some science journals that claim to peer review papers do not do so," 21 June 2018 These ranged from fungi and lichens, through herbaceous and woody plants to nematodes, insects, bats and passerine birds. John Healey, John Halley And Kalliopi Stara, Smithsonian, "Sacred Sites Can Also Be Hotspots of Conservation," 17 May 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'lichen.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

See More

First Known Use of lichen

circa 1657, in the meaning defined at sense 2

History and Etymology for lichen

Latin, from Greek leichēn, lichēn, from leichein to lick

Keep scrolling for more

Learn More about lichen

Dictionary Entries near lichen


lich bird





lichen green

Statistics for lichen

Last Updated

14 Nov 2018

Look-up Popularity

Time Traveler for lichen

The first known use of lichen was circa 1657

See more words from the same year

Keep scrolling for more

More Definitions for lichen



English Language Learners Definition of lichen

: a type of small plant that grows on rocks and walls


li·​chen | \ˈlī-kən \

Kids Definition of lichen

: a plantlike organism made up of an alga and a fungus growing together


li·​chen | \ˈlī-kən \

Medical Definition of lichen 

1 : any of several skin diseases characterized by the eruption of flat papules especially : lichen planus

2 : any of numerous complex plantlike organisms made up of an alga and a fungus growing in symbiotic association on a solid surface (as a rock)

Keep scrolling for more

Comments on lichen

What made you want to look up lichen? Please tell us where you read or heard it (including the quote, if possible).


full of whispering sounds

Get Word of the Day daily email!

Test Your Vocabulary

Difficult Vocab Quiz

  • the-education-of-achilles-eugne-delacroix
  • Which is a synonym of discomfit?
True or False

Test your knowledge - and maybe learn something along the way.

Word Winder's CrossWinder

Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!