| Word | Description |
| X Standards | A series of evolving recommendations covering data networks. |
| X12 | An accepted standard for using EDI. It allows organisations to exchange data electronically using their own normal form layout. |
| X400 | An example of a standard that allows electronic messages to be sent from one computer to another regardless of hardware and software differences. |
| xDSL (digital subscriber line) | A generic name encompassing many variants of DSL technology such as ADSL, HDSL and VDSL. |
| XML (extensible mark-up language) | A language that is used to describe the structure of data. |