Geometric Dimensioning and Tolerancing [GD&T]
Geometric dimensioning and tolerancing is the practice of conveying manufacturing geometry and tolerances in a concise and standardized method.

To be concise the engineer must use symbols to reduce potentially misleading or vague written descriptions.  Understanding the symbols allows the engineer insight to design intent (functionality).

The table below shows the 14 primary symbols used  to describe allowable characteristic variation per the 1994 standard.

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