| Synergism is the act of working together. | (Environmental Engineering) Two chemicals which are synergistic have a greater effect together than the sum of their individual effects. The effect can be either positive or negative. |
| Thermocline | (Environmental Engineering) The depth at which an inflection point occurs in a lake temperature profile. |
| Trickling filter | (Environmental Engineering) An attached growth biological process in which the microbial film is attached to non-moving rock or plastic media. |
| Troposphere | (Environmental Engineering) The lower atmosphere, from the earth's surface to approximately 12 km. This portion of the earth's atmosphere contains about 95 percent of the atmospheric gases. The temperature gradually declines through this region. |
| Ultimate disposal | (Environmental Engineering) The process of returning residuals back to the environment in a form which will have the minimal or reduced negative environmental impacts. |
| Weak acid | (Environmental Engineering) An acid that does not ionize completely under the conditions of interest. Examples include acetic acid, carbonic acid, and hypochlorous acid. See strong acid. |
| Adaptive maintenance - | (Software Engineering) activity associate with changing an application to make it conform to changes in its external environment |
| Agile development (also referred to as agile process model) - | (Software Engineering) an adapted version of software engineering that emphasizes customer communication, incremental software delivery, informal methods and work products, and highly motivated teams. |
| Black box testing - | (Software Engineering) testing that does not focus on the internal details of the program but uses external requirements |
| Boundary value analysis - | (Software Engineering) a black box testing method that designs test cases that exercise data boundaries |