Cilium

Part of speech: noun

Pronunciation: /ˈsɪl.i.əm/

Definitions

1. A microscopic hair-like structure that extends from the surface of certain cells and moves back and forth to generate fluid movement or enable cellular locomotion
2. A slender, hair-like projection from the surface of cells that plays a role in movement or fluid displacement within biological systems
3. A tiny, hair-like appendage found on cell surfaces that aids in cell movement and the circulation of fluids in their environment

Etymology: Before it named the tiny hairs that line the cells of our airways, "cilium" simply meant "eyelid" in Latin. The Latin word was built from an ancient root for "to cover" or "to conceal," which also gave rise to words for things that shield or hide. The eyelash sense, the one that made the word famous, came later in the scientific tradition that borrowed it. When English took the word, it kept the original Latin sense of the eyelid's margin and fringe, so the eyelash was never far from its meaning. Biologists then applied it to the microscopic hair-like projections that beat rhythmically on cell surfaces, a sense English adopted directly from Latin, with the spelling and form unchanged.

Synonyms: hair, flagellum