The types of numeric constraints that can be applied to sketches are called dimensional constraints, which can be represented as numerical constants, algebraic equations containing variables or linked parametric files. Examples of these constraints include diameter dimension, horizontal dimension, radial dimension and vertical dimension.
In engineering and computer-aided design, constraints are limiting factors or conditions imposed to define the size, shape, location and correlations among sketch elements in a modeling system. Constraints are classified into two types: dimensional and geometric.
Dimensional constraints control the size of the sketch. Modifying the dimensions results in a change in the size of the elements comprising the sketch, such as lines, rectangles, points, arcs, ellipses and circles.