| Internal force: | (english) Forces which hold an object together when external forces or other loads are applied. Internal forces are sometimes called resisting forces since they resist the effects of external forces. |
| Shear: | (english) An system of internal forces whose resultant is a force acting perpendicular to the longitudinal axis of a structural member or assembly: sometimes called shear force. |
| Statically determinate: | (english) A statically determinate structure is one where there is only one distribution of internal forces and reactions which satisfies equilibrium. In a statically determinate structure, internal forces and reactions can be determined by considering nothing more than equations of equilibrium. |
| Statically equivalent: | (english) Two force systems are statically equivalent when their resultants are equal. Physically, this means that the force systems tend to impart the same motion when applied to an object; note that the distribution of resulting internal forces in the object may be different. |
| Statically indeterminate: | (english) A statically indeterminate structure is one where there is more than one distribution of internal forces and/or reactions which satisfies equilibrium. |
| Stress: | (english) The intensity of internal force acting at a point in an object. Stress is measured in units of force per area. See shear stress and normal stress. |
| Black box testing - | (Software Engineering) testing that does not focus on the internal details of the program but uses external requirements |
| Make-buy decision - | (Software Engineering) determining whether software should be built internally, acquired, contracted or built from reusable components |
| Refactoring - | (Software Engineering) changing software in a way that improves its internal structure but does not change it external behavior; often conducted iteratively as design evolves into code. |
| Security - | (Software Engineering) the ability of software to operate in a manner that is secure from internal or external attack |