| Word | Description |
| Facet | One triangular element used to approximate the surface of a model. A facet is defined as three nodes and an outward normal. It takes thousands of triangles to define a complex model. The facet data is kept in an STL file. |
| Facet Deviation | Maximum distance between the triangular element of an STL file and the surface that it approximates. See also chord height. |
| Family Mold | Tool that has cavities for two or more different parts. |
| Feature | Discrete attributes of a model or prototype that include holes, slots, ribs, bosses, snap fits and other basic elements of a product design. |
| Fit & Form | Shape and size of a component and its relationship to mating components. Often used in the context of design analysis of the adequacy of a part in terms of its size, shape and conformance to constraints imposed by mating or nested components. |
| FOB | FOB, is an abbreviation for Free On Board. The term commonly used when shipping goods, to indicate who pays loading and transportation costs, and/or the point at which the responsibility and ownership of the goods transfers from shipper to buyer. |
| Founndry | A foundry is a factory which produces castings of metal, both ferrous and non-ferrous. |
| Fused Deposition Modeling | A thermoplastic extrusion-based rapid prototyping technology. |