Euclid — "To describe a circle with any centre and radius."

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

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

"Further, of trilateral figures, a right-angled triangle is that which has a right angle, an obtuse-angled triangle that which has an obtuse angle, and an acute-angled triangle that which has its three…"

"No trace of Euclid's personality has survived."

"If a straight line be cut into two equal parts and also into two unequal parts, the rectangle contained by the unequal parts together with the square on the line between the points of section is equal…"