Geometric dimensioning and tolerancing (GD&T) is a symbolic language used to communicate the allowable variation within a product assembly and standardizes variations in measurement. Size tolerances define the allowable variation in the size of a feature, while form tolerances describe the allowable variations in the contours of features and surfaces on a part. In this interactive, online course, we will discuss size tolerances, and form tolerances, as well as cylindricity, and circularity.