1. of or relating to Euclid or the geometry based on his axioms and postulates, in which space is flat and parallel lines never meet
Usage: mathematics; often capitalized
2. of or relating to ordinary three-dimensional space as opposed to curved or higher-dimensional space
Usage: mathematics; physics

Examples

• In euclidean geometry, the angles of a triangle always sum to 180 degrees.
• The classroom floor represents a euclidean plane where parallel lines never intersect.
• Non-euclidean geometry challenges the assumptions of euclidean space.
• Most everyday measurements and constructions rely on euclidean principles.
• Einstein's theory of relativity showed that space is not purely euclidean at cosmic scales.