it is a nonnumerical relationships between the parts of a geometric figure. Examples include parallelism, perpendicularity, and concentricity.
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Geometric constraints occur for dimensioning and tolerancing mechanical parts in
http://www.chacha.com/question/whataregeometric...

Geometric engineers are civil engineers who use computeraided design to create roads, bridges and other forms of infrastructure using geometric design and patterns. Geometric engineers
http://www.ehow.com/info_10035350_geometricengine...

geometric constraint  is set relative to other geometry (ie must be smaller or bigger than etc) numeric constraint  is set as a hard number. not dependent on anything.
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