"A diameter of the circle is any straight line drawn through the center and terminated in both directions by the circumference of the circle, and such a straight line also bisects the circle."

"Of trilateral figures, an equilateral triangle is that which has its three sides equal, an isosceles triangle that which has only two of its sides equal, and a scalene triangle that which has its thre…"

"Rectilineal figures are those which are contained by straight lines..."

"A quantity is said to be a part of a quantity, the less of the greater, when it measures the greater."

"The square on the side subtending the right angle in right-angled triangles is equal to the squares on the sides containing the right angle."