| Mixed liquor suspended solids (MLSS) | (Environmental Engineering) The total suspended solids concentration in the activated sludge tank. |
| Mixed liquor volatile suspended solids (MLVSS) | (Environmental Engineering) The volatile suspended solids concentration in the activated sludge tank. |
| Refuse derived fuel (RDF) | (Environmental Engineering) A fuel derived from the combustible portion of municipal solid waste. The fuel is often processed into small briquettes, similar in size to charcoal. |
| Total dissolved solids | (Environmental Engineering) (TDS) is the amount of dissolved matter in the water. |
| Total solids | (Environmental Engineering) (TS) is the amount of organic and inorganic matter which is contained in a water. |
| Total suspended solids | (Environmental Engineering) (TSS) is the amount of suspended (filterable) matter in a water. |
| Volatile solids | (Environmental Engineering) (VS) is the amount of matter which volatilizes (or burns) when a water sample is heated to 550EC.Volatile suspended solids |
| Requirements engineering - | (Software Engineering) the activities required to elicit, elaborate, negotiate, specify, and validate system or software requirements |
| Software Requirements Specification - | (Software Engineering) a deliverable that describes all data, functional and behavioral requirements, all constraints, and all validation requirements for software |
| Validation - | (Software Engineering) tests to ensure that the software conforms to its requirements |