The general content of the thirteen books of Euclid's Elements is:
I: Constructions, congruence, area, Pythagorean Theorem.
II: Geometry as it applies to algebra.
III: Geometry of the circle.
IV: Constructions of polygons.
V and VI: Proportions and similar figures.
VII, VIII and IX: Number Theory.
x: Irrational numbers.
XI-XIII: Solid geometry dealing with volume, area, and construction.
The method of developing and presenting ideas in the Elements is carried out in a very systematic way that came to characterize Greek mathematics. Euclid first established definitions for basic terms and concepts. Some of them are listed here: