A living organism made of fungus and algae living together, often found as a colorful crust on rocks or tree bark.
From Greek 'leichein' (to lick), because lichen appears to lick or coat rocks. The organism itself was not understood as a symbiosis until the 1860s—before that, scientists thought it was a single plant.
Lichen is one of nature's original partnerships—the fungus provides structure and water, the algae provides food through photosynthesis—a 1.4-billion-year-old cooperation that literally built soil from bare rock.
Complete word intelligence in one call. Free tier — 50 lookups/day.