Book:Euclid/The Elements/Book V

Contents
Book $\text{V}$: Theory of Proportions
 * Definitions



Comment
With the development of algebra and the definition of a ratio as a fraction, and a proportion as an equality of ratios, the importance of this book has been considerably reduced.

As Augustus De Morgan put it:
 * ...simple propositions of concrete arithmetic, covered in language which makes them unintelligible to modern ears.

The modern student of mathematics, having been raised on the definition of rational numbers in the context of field theory, is perhaps excused for considering this book as little more than pointless piffle.