meniscus

/məˈnɪskəs/

/məˈnɛskɪs/

Other forms: menisci

The next time you pour some fluid into a tube, look at it from the side. You will see the liquid has a slight curve, either up or down. This curved surface, created by air pressure, is called a meniscus.

The Greeks had a word for the lunar crescent, mēniskos, which itself came from the word for the moon, mḗnē. In the late 17th Century, the word meniscus was given to similarly-curved lenses. Then in 1812, the curved surfaces of liquid were referred to by this word as well. Later, the name was also applied to a crescent-shaped cartilage at the knee, between the tibia and the femur. These small, semi-lunar bits are important for reducing friction during leg movement.

Definitions of meniscus

1. noun

   (optics) a lens that is concave on one side and convex on the other
   type of:

   lens, lens system, lense

   a transparent optical device used to converge or diverge transmitted light and to form images
2. noun

   (physics) the curved upper surface of a nonturbulent liquid in a vertical tube
   type of:

   surface

   the outer boundary of an artifact or a material layer constituting or resembling such a boundary
3. noun

   (anatomy) a disk of cartilage that serves as a cushion between the ends of bones that meet at a joint
   synonyms: semilunar cartilage

   type of:

   cartilage, gristle

   tough elastic tissue; mostly converted to bone in adults