# What is MathML?

Source: https://epublab.com/glossary/mathml/ (updated 2026-11-03)

MathML is the XML language for mathematical notation, allowed inside EPUB 3 content documents so equations stay text instead of images. Support in reading apps varies.

## Why it matters when you convert a PDF to EPUB

A PDF draws an equation as positioned glyphs and lines, with no record of its structure. Rebuilding MathML from that is hard; a converter that cannot do it reliably should keep the equation's text in order rather than produce wrong mathematics. EPUBCheck asks MathML to carry alternative text (ACC-009).