Strain measures for hyperelastic materials must model the effect of finite deformations. They are single-based second-order tensors, either Eulerian or Lagrangian, and are defined in terms of the Cauchy-Green deformation tensors, which are derived from the deformation gradient. The Green-Lagrange strain tensor is Lagrangian based, while the Almansi strain tensor is Eulerian based. Both of these strain measures are described in detail. The Green-Lagrange strain tensor is in terms of the right Cauchy-Green deformation tensor, while the Almansi strain tensor is in terms of the left Cauchy-Green deformation tensor. The reduced invariants of the right and left Cauchy-Green deformation tensors, known as the invariants of the right and left Cauchy-Green distortion tensors, are introduced, and the derivation of the reduced invariants is presented and defined. Since the strain measures are derived from the deformation gradient, they are related, the relationship is easily demonstrated. An additional strain measure, one which is less commonly employed, is the Biot strain tensor. The different strain measures can be formally reduced to those of linear elastic systems, this being demonstrated.