: 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
Recent Examples on the WebNow, however, almost every surface is covered in bird poop as the new tenants moved in, and cracks are appearing in the concrete as lichens, mold and other plant life grows.—Owen Bellwood/jalopnik, Quartz, 27 July 2024 No one knows this better than lichenologists, who study the symbiosis between fungi, algae and other microbes that form lichens.—Corrado Nai, Smithsonian Magazine, 25 June 2024 Race on the White River, learn about lichens, or go on a night hike with these events around the state.—Karl Schneider, The Indianapolis Star, 13 June 2024 While working on a project about lichen symbiosis, Smith learned that many moth species blend in with lichen—such as the Merveille du Jour moth, which is now tattooed on their forearm.—Allison Parshall, Scientific American, 14 May 2024 See all Example Sentences for lichen
These examples are programmatically compiled from various online sources to illustrate current usage of the word 'lichen.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.
Word History
Etymology
Latin, from Greek leichēn, lichēn, from leichein to lick
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