Meniscus Defined

The word "meniscus" derives from the Greek word for "crescent." The meniscus can refer to the curvature of liquid, the anatomy of a knee or a lens to reduce distortion.

Liquids

• A meniscus forms on a standing body of liquid in a glass container, such as a graduated cylinder used in science labs. A meniscus can be concave or convex. A concave meniscus forms when a liquid's molecules attract or adhere to those of the container. Capillary action will pull the liquid up the sides for a U-shaped meniscus. When measuring, the eye should be level with the horizontal center of the meniscus. The bottom of the meniscus should be read.

  By contrast, a convex meniscus forms when the liquid's molecules have a stronger attraction or cohesion to each other than to the container. For example, mercury in a thermometer will have a convex meniscus with the center positioned at the top edge.

Knee

• Each knee contains two menisci: the medial (inside) meniscus and the lateral (outside) meniscus. According to the U.S. National Library of Medicine, the meniscus helps lubricate the knee joint, absorbs shock, allows proper weight distribution and limits the flexing and extending of the joint. The medial meniscus resembles a "C" shape, while the lateral meniscus resembles an incomplete circle.

Lenses

• Meniscus lenses help reduce beam distortion in certain applications, such as focusing light beams through a telescope. The lens has both convex and concave sides. In condenser systems, this lens is part of an enlarger used to transmit light through photographic negatives in the photo darkroom.