constraint

In mechanics, constraints are conditions that limit the motion or behavior of a system. These can be explicit, like a body being restricted to move along a surface, or implicit, such as the rigidity of an object. Constraints are often handled by introducing new mathematical concepts and techniques, like configuration space, which is a multidimensional space where each point represents the complete state of a system. This approach allows for a more manageable description of complex systems, especially when dealing with forces that are difficult to model directly. For instance, the constraint of rigidity reduces the number of independent variables needed to describe a body from 3N (for N atoms) to just 6. Constraints can also be understood more generally as restrictions or limitations on actions or choices.12