| Racking: | (english) The distortion of a rectangular shape to a skewed parallelogram. |
| Section Modulus: | (english) A property of a cross sectional shape, which depends on shape, and orientation. Section modulus is usually denoted S, and S = I/c, where I = moment of inertia about an axis through the centroid, and c is the distance from the centroid to the extreme edge of the section. |
| 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. |
| 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. |
| Structural model: | (english) An idealization for analysis purposes of a real or conceived structure. A structural model includes boundaries limiting the scope of the analysis. Supports occur at these boundaries, representing things which hold the structure in place. |
| Advanced wastewater treatment | (Environmental Engineering) The removal of any dissolved or suspended contaminants beyond secondary treatment, often this is the removal of the nutrients nitrogen and/or phosphorus. |
| Attached growth reactor | (Environmental Engineering) A reactor in which the microorganisms are attached to engineered surfaces within the reactor. Examples of attached growth reactors are the trickling filter and the rotating biological contactor. See suspended growth reactor. |
| Autotrophs | (Environmental Engineering) A group of organisms capable of obtaining carbon for synthesis from inorganic carbon sources such as carbon dioxide and its dissolved species (the carbonates). This group includes plants and algae. |
| Biochemical oxygen demand (BOD) | (Environmental Engineering) The amount of oxygen required to oxidize any organic matter present in a water during a specified period of time, usually 5 days. It is an indirect measure of the amount of organic matter present in a water. |
| CFCs | (Environmental Engineering) Chlorofluorocarbons, chemicals which result in a depletion of the ozone layer in the upper atmosphere. |