| Ultimate biochemical oxygen demand (BODu) | (Environmental Engineering) The total amount of oxygen required to oxidize any organic matter present in a water, i.e. after an extended period, such as 20 or 30 days. |
| 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. |
| UML (Unified Modeling Language) - | (Software Engineering) a comprehensive diagrammatic notation for the analysis and design of software |
| Unified process - | (Software Engineering) a "use-case driven, architecture-centric, iterative and incremental" software process that emphasizes the use of UML notation |
| Unit testing - | (Software Engineering) part of the testing strategy that focuses on tests to individual program components |
| Usability - | An informal measure of the ease with which a user interface can be learned and applied with efficiency and without errors |
| Use-case - | (Software Engineering) a written description that defines a very specific interaction between a user and a system, often (but not always) written in the form of a usage scenario |
| User - | (Software Engineering) the person who actually used to software or the product that has software embedded within it |
| User hierarchy - | (Software Engineering) a hierarchical representation of the categories of users that will interact with any type of software |
| User-story - | (Software Engineering) a usage scenario that is used as part of Extreme programming |