Sylvester-Gallai theorem

Etymology
Named after, who posed it as a problem in 1893, and , who published one of the first proofs of this theorem in 1944.

Proper noun

 * 1)  A theorem stating that, given a finite number of points in the Euclidean plane, either all the points lie on a single line, or there is at least one line which contains exactly two of the points.