What does sessile mean?
Sessile means attached directly to a surface or otherwise fixed in one place. The word is used especially in biology to describe organisms that cannot readily move away from their substrate: corals, barnacles, mussels, and many small marine organisms may be sessile, as are plants whose leaves or flowers grow directly from a stem without a stalk. The word comes from Latin sessilis, meaning “sitting” or “attached,” and ultimately reflects the idea of remaining seated in place. Sessile is a precise alternative to vague descriptions such as “stationary” because it specifically suggests physical attachment as well as an inability to move. In figurative use, it can describe anything that is firmly established or fixed, though the scientific sense remains its dominant use.
adjectiveAttached directly to a surface or substrate and unable to move away from it. In biology, the term describes organisms that remain fixed in place for much or all of their lives.
- In biology, attached to a surface or substrate and unable to move from it.
- In botany, attached directly to a substrate rather than borne on a stalk.
"Many reef-building corals are sessile, attaching themselves permanently to the ocean floor."
"Barnacles are sessile organisms that remain attached to rocks and ship hulls."
"The plant has sessile flowers, with each bloom attached directly to the stem."
A coral colony can build an elaborate underwater landscape while remaining sessile, anchored to the seafloor for life.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does sessile come from?
Sessile entered English in the early 17th century from the Latin adjective sessilis, meaning “sitting,” “attached,” or “dwelling in place.” The Latin word was formed from sedere, “to sit,” the source of related terms such as sedentary, reside, and subsidy. Its development in English preserved the idea of being fixed or attached rather than actively moving.
How sessile is actually used
Primarily a formal scientific term. In biology, it contrasts with motile and is especially common in descriptions of animals, plants, fungi, and microorganisms that remain attached to a surface.