plane geometry

/pleɪn dʒiˌɑmətri/

In math, plane geometry is a system of measuring flat, two-dimensional shapes. If you use a protractor to measure the angle of a triangle, you're doing plane geometry!

Plane geometry is also called Euclidean geometry, after the ancient Greek mathematician Euclid, who's credited with inventing it. This kind of math is all about lines, triangles, squares, parallelograms — any shape that can be drawn on paper. In plane geometry, you learn things like calculating the area of a rhombus and the circumference of a circle. A plane is a flat surface, and geometry comes from Greek roots meaning "measurement of earth."

Definitions of plane geometry

1. noun

   the geometry of 2-dimensional figures
   type of:

   geometry

   the pure mathematics of points and lines and curves and surfaces