| Abbreviation | Definition |
|---|---|
| TXT | Text |
| TXX | Text Control ActiveX |
| TYJ | Teach Yourself Java |
| TYT | Tae Young Telstar |
| U | Undefined |
| U | Unicode |
| U | Update |
| U | User |
| U | Users |
| U/lc | Upper/Lower Case typeset |
| UA | Unnumbered Acknowledgement |
| UA | User Agent |
| UAE | Unrecoverable Application error |
| UAG | Unmanned Aircraft General |
| UART | Universal Asynchronous Receiver/ Transmitter |
| UAU | Unix for Advanced Users |
| UAX | Unicode Standard AnneX |
| UAX-1 | Unicode Standard AnneX 1, Burmese, Khmer, Ethiopian ( Superceded by Unicode Standard Version 3.0) |
| UAX-10 | Unicode Standard AnneX 10, Unicode Collation Algorithm |
| UAX-11 | Unicode Standard AnneX 11, East Asian Width |