The difference between cavity dimensions and part dimensions after molding is called Linear Shrinkage.
It can be influenced by restrains of the mold, crystallinity and orientation.
The orientation occurs due to shear and extensional forces in the polymer and fillers (if the material contains fillers) during filling and packing phase.
The direction and magnitude of the orientation may vary and has a direct effect on the shrinkage.
This glossary of plastic industry is provided by PLEXPERT Canada Inc.