Final answer:
René Descartes' significant contribution to geometry is the development of the Cartesian coordinate system, which is fundamental to Cartesian geometry.
Step-by-step explanation:
The contribution to geometry that is attributed to the work of René Descartes is the development of the Cartesian coordinate system. This system revolutionized the way we think about geometry by providing a systematic method of labeling each point on a plane with a pair of numbers. These contributions are central to what is known as Cartesian geometry, which includes the concept of plotting graphs using an x-y coordinate system. Descartes' method made a profound impact on the study and application of geometry and has become a fundamental tool in mathematics, physics, engineering, and many other disciplines.