the geometry of figures whose parts all lie in one plane.
Origin of plane geometry
First recorded in 1740–50
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the study of the properties of and relationships between plane curves, figures, etc
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
The mathematical study of geometric figures whose parts lie in the same plane, such as polygons, circles, and lines.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
The study of two-dimensional figures (figures that are confined to a plane).
Plane geometry is one of the oldest branches of mathematics.
The Greek mathematician Euclid was the first to study plane geometry carefully. His book Elements was the standard plane geometry textbook for centuries.
The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.