Solids behave differently when they are subjected to large deformations as opposed to small ones. This is due to the change in their shape and it often introduces a form of nonlinearity known as geometric nonlinearity. The degree to which this nonlinearity affects the solution accuracy is controlled by certain variables, including the nature of the loading, the material used, boundary conditions, etc.; While using small deformation theory to solve for a structure’s response is inexpensive, it may be inaccurate when this nonlinearity is prominent. In this Ansys Innovation Course on “Large Deformations”, we will introduce the physical nature of large deformations and how they are captured mathematically. We will present the simplifying assumptions that are made when we use small deformation theory and the impact they have on the accuracy of a solution using several examples. Completing this course will enable you to answer a simple but very important question: When do we use large deformation theory to analyze a structure’s response?