Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In algebraic geometry Mazur''s torsion theorem, due to Barry Mazur, classifies the possible torsion subgroups of the group of rational points on an elliptic curve defined over the rational numbers. If Cn denotes the cyclic group of order n, then the possible torsion subgroups are Cn with 1 n 10, and also C12; and the direct sum of C2 with C2, C4, C6 or C8.