This page will be under constant revision so please use the reload button on your browser to refresh the page. The primary difference has to do with the parallel postulate. Non-Euclidian geometries can allow no parallel lines thru the point or an infinite number of parallel lines. A straight line can be continued indefinitely. With any point as center, a circle with any radius may be described.
All right angles are equal.
If equals are added to equals, the wholes are equal. If equals are subtracted from equals, the remainders are equal. Things which coincide with one another are equal. The whole is greater than a part. From his postulates and notions, Euclid deduced 465 theorems.