| Vector: | (english) A mathematical entity having a magnitude and a direction in space. |
| Velocity: | (english) A vector quantity equal to the rate that position changes with time. |
| 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. |
| 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. |
| Alcohol | (Environmental Engineering) An organic compound with one or more hydroxyl "-OH" groups. |
| Aldehyde | (Environmental Engineering) An organic compound with a carbonyl at one end of a hydrocarbon group. |