noun
lichen
LEYE-kuhn
noun
1
A slow-growing organism formed by algae and fungi living together, often seen as pale or greenish patches on rocks, trees, or walls.
"Thick lichen covered the old stone wall."
"Scientists study lichen because it's sensitive to air pollution."
How to Use Lichen
Learner’s notesIn plain EnglishA crusty or leafy organism, part fungus and part alga, that grows on rocks, bark, and similar surfaces.
Common pairings
lichen-covered
a patch of lichen
Word Forms
lichened past tense, lichens plural, lichen plural, lichens singular
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Etymology
From Latin lichen, from Ancient Greek leikhḗn, related to leíkhō, "to lick" — the name likely comes from how the growths seem to "lick" or spread across a surface.