"Trilateral figures are those contained by three straight lines, quadrilateral those contained by four, and multilateral those contained by more than four straight lines."

"The greatest common divisor of two numbers can be found by successive division."

"The angles in the same segment are equal to one another."

"A surface is that which has length and breadth only."

"Parallel straight lines are straight lines which, being in the same plane and being produced indefinitely in both directions, do not meet one another in either direction."