1. A branch of geometry that rejects Euclid's parallel postulate, including hyperbolic and elliptic geometries where the sum of angles in a triangle does not equal 180 degrees.
Non-Euclidean geometry is essential to Einstein's theory of general relativity.
A geometria não-euclidiana é essencial para a teoria da relatividade geral de Einstein.
2. Any geometric system based on alternative axioms to those of Euclidean geometry, allowing for curved spaces.
The mathematician studied non-Euclidean geometry to understand the structure of space-time.
O matemático estudou geometria não-euclidiana para compreender a estrutura do espaço-tempo.