Euclidean geometry is a branch of mathematics that deals with the study of flat space and shapes. This type of geometry was developed by the ancient Greek mathematician Euclid, hence its name. If you want to refer to Euclidean geometry without using the term "Euclidean," you could use several synonyms such as classical geometry, plane geometry, or flat geometry. These terms all refer to the same concepts and principles as Euclidean geometry, but provide an alternative way to describe this branch of mathematics. Other related terms that could be used as synonyms include geometric algebra, synthetic geometry, and ruler-and-compass construction.