| Weight: | (english) The force on an object resulting from gravity. |
| Yield stress: | (english) A material loaded beyond its yield stress, no longer exhibits linear elastic behavior. Metals, particularly mild steel, generally have a very well defined yield stress compared to other materials. Yield stress is sometimes called yield strength. |
| Yield strain: | (english) A material deformed beyond its yield strain, no longer exhibits linear elastic behavior. See yield stress. |
| Adsorption | (Environmental Engineering) A surface phenomena in which a solute (soluble material) concentrates or collects at a surface (the adsorbent). |
| 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. |
| Aerobes | (Environmental Engineering) Organisms which require molecular oxygen as an electron acceptor for energy production. See anaerobes. |
| Aerobic process | (Environmental Engineering) A process which requires molecular oxygen. |
| Aldehyde | (Environmental Engineering) An organic compound with a carbonyl at one end of a hydrocarbon group. |
| Amino acid | (Environmental Engineering) A functional group which consists of a carbon with a carboxylic acid, "-COOH" and an amine, "-NH2." These compounds are the building blocks for proteins. |
| Anabolism | (Environmental Engineering) Biosynthesis, the production of new cellular materials from other organic or inorganic chemicals. |