| 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. |
| Autotrophic | (Environmental Engineering) Organisms which utilize inorganic carbon for synthesis of protoplasm. Ecologists narrow the definition further by requiring that autotrophs obtain their energy from the sun. In microbiologist parlance, this would be a photoautotroph. See photoautotrophic and chemoautotrophic. |
| Biofilm | (Environmental Engineering) A film of microorganisms attached to a surface, such as that on a trickling filter, rotating biological contactor, or rocks in natural streams. |
| Consumers | (Environmental Engineering) Organisms which consume protoplasm produced from photosynthesis or consume organisms from higher levels which indirectly consume protoplasm from photosynthesis. |
| Heterotrophic | (Environmental Engineering) A group of organisms which obtain carbon for synthesis from other organic matter or proteins. |
| Metabolism | (Environmental Engineering) The processes which sustain an organism, including energy production, synthesis of proteins for repair and replication. |
| Organic nitrogen | (Environmental Engineering) Nitrogen contained as amines in organic compounds such as amino acids and proteins. |
| Photoautotrophic | (Environmental Engineering) Organisms which utilize inorganic carbon dioxide for protoplasm synthesis and light for an energy source. See autotrophic and chemoautotrophic. |
| Producers | (Environmental Engineering) Autotrophic organisms which produce protoplasm using inorganic carbon and energy from the sun. |
| Paper prototype - | (Software Engineering) a paper representation of an application (e.g., story boards that describe the interaction at a human interface) |