Geometric Dimensioning and Tolerancing (GD&T) is a system of symbols, rules, and definitions used to specify and control the form, orientation, and location of features on a part or assembly. GD&T is used to communicate design requirements and manufacturing tolerances in a precise and unambiguous way.

GD&T includes symbols and language for specifying geometric features such as flatness, parallelism, perpendicularity, circularity, cylindricity, and positional tolerance. It also includes rules for defining datum features and datum references, which are used to establish a reference coordinate system for the part or assembly.

One of the main benefits of using GD&T is that it allows for more precise and consistent communication of design requirements and manufacturing tolerances. This helps to reduce errors and rework, and ensures that parts and assemblies meet the desired specifications.

GD&T is commonly used in industries such as aerospace, automotive, and manufacturing, where precise tolerances and high-quality standards are required. It is also widely used in engineering drawings and specifications.

To become proficient in GD&T, it is recommended to take training courses and obtain certification from organizations such as the American Society of Mechanical Engineers (ASME) or the Society of Manufacturing Engineers (SME).