Allows a number of useful mathematical simplifications and approximations. Finite Strain Strain larger than a few percent. Requires a more complicated mathematical treatment than infinitesimal strain. Homogeneous Strain Uniform strain. Straight lines in the original object remain straight.
Parallel lines remain parallel.
Circles deform to ellipses. Note that this definition rules out folding, since an originally straight layer has to remain straight. How real geology behaves. Deformation varies from place to place. Lines may bend and do not necessarily remain parallel.