| isometric view | รูปไอโซเมตริก |
| isotropic | คุณสมบัติเหมือนกันทุกทิศทาง |
| iteration | การหาคำตอบโดยวิธีแทนค่าคำนวนซ้ำ |
| Inelastic: | (english) Not surprisingly, the opposite of elastic. A deformation of a structure or material under load is described as inelastic when the deformation remains after the load is removed. The term plastic is often used with the same meaning. |
| Inertia: | (english) The tendency of an object at rest to remain at rest, and of an object in motion to remain in motion. |
| Inertial Force: | (english) A fictitious force used for convenience in visualizing the effects of forces on bodies in motion. For an accelerating body, the inertial force is considered as a body force whose resultant acts at the object's center of gravity in a direction opposite the acceleration. The magnitude of the force is the mass of the object times the magnitude of the acceleration. |
| 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. |
| In situ treatment | (Environmental Engineering) Treatment of a waste in place, as opposed to pumping or digging the waste up and then treating it. |
| Infectious disease | (Environmental Engineering) A disease caused by pathogenic organisms. |
| Influent | (Environmental Engineering) The fluid entering a system, process, tank, etc. An effluent from one process can be an influent to another process. See effluent. |