X

A symbol used to show where something or someone should be placed or located.

XML

eXtensible Markup Language. A programming language/specification developed by the W3C. XML is a pared-down version of SGML, designed especially for Web documents. It enables Web authors and designers to create their own customized tags to provide functionality not available with HTML.

X-ray

A means of showing photographically the inner workings of parts or material which is otherwise opaque to the eye.