What does planarity mean?
Planarity is the condition of being flat or two-dimensional, with every point lying in the same plane. The word is used particularly in geometry, engineering, and technical design when discussing whether a surface or figure has this property. It also has an important specialized meaning in graph theory: a graph possesses planarity if its edges can be drawn in a plane so that they meet only at their shared endpoints. Thus, questions about planarity can determine whether a network, circuit, or diagram can be represented without unwanted intersections. Outside technical contexts, the ordinary word “flatness” is usually more approachable. Although planarity is sometimes treated as an uncountable property, the plural “planarities” is grammatically possible when different objects or cases are being discussed individually.
nounThe quality or state of being planar, especially of having all points contained in a single plane. In graph theory, it denotes the property of a graph being drawable in a plane without any edges crossing except at shared endpoints.
- The state or quality of being planar or having all its points in one plane.
- The property of a graph being drawable in a plane without crossings other than at shared endpoints.
"The engineer tested the planarity of the surface before beginning the installation."
"The planarity of the design allows it to be manufactured from a single sheet."
"The algorithm determines the planarity of a graph in linear time."
Usually treated as an uncountable property; the plural is rare and appropriate when different instances are discussed individually.
"The researchers compared the planarity of several thin sections."
In graph theory, planarity decides whether a network can be drawn on one flat page without crossing lines—a surprisingly consequential geometric question.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does planarity come from?
“Planarity” was formed in English by combining “planar” with the suffix “-ity.” “Planar” comes from Latin “planus,” meaning “level,” “flat,” or “even.” The Latin word also underlies English “plane” and related mathematical terms such as “planimetry.”
How planarity is actually used
This is chiefly a mathematical and technical term. In everyday speech, “flatness” is more natural.
Easily confused with planarity
“Planarity” is the quality of being flat or two-dimensional, whereas “planes” refers to flat surfaces or the plural of “plane.”