UX Glossary

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X-Height XML (Extensible Markup Language) XSL (Extensible Stylesheet Language)
X-Height XML (Extensible Markup Language) XSL (Extensible Stylesheet Language)

X-Height

The height of the lowercase letter "x" in any given font. Larger x-heights make the font appear larger and hence increase readability.

https://usabilitest.com/glossary/x-height