Constraints are imposed conditions, rules or limiting factors. Geometric and numeric constraints occur in engineering and computer-aided design, with applications in a number of mechanical design areas, including architectural drafting and robotics. There is a clear difference between a geometric constraint and a numeric constraint. Simply put, a geometric constraint relates to other parts of a geometric figure, whereas a numeric constraint is a set number not relative to other parts of a design. Both geometric and numeric constraints define the dimensions of objects in computer-aided design, or CAD, modeling systems.