Geometric Dimensioning and Tolerancing (GD&T) is a system used in engineering and manufacturing to define the allowable variations in the size and shape of parts. It provides a clear and concise way to communicate how parts should be manufactured and assembled, ensuring they fit together correctly. GD&T uses symbols and annotations on technical drawings to specify geometric features, such as flatness, roundness, and parallelism. By using GD&T, engineers can improve the quality of their designs and reduce production costs. This system helps to minimize misunderstandings between designers and manufacturers, leading to more efficient processes and better product performance.