Role of <mfrac>
Builds a structured fraction. Use the element for its semantic role rather than as a visual styling shortcut. Assistive technology, browser math layout, conversion tools, and copy-and-paste behavior all depend on the markup preserving the mathematical structure.
Example markup
<mfrac><mi>a</mi><mi>b</mi></mfrac>Allowed children
exactly two child expressions
Only place children inside <mfrac> when they match the element's content model. Validate the complete MathML tree after conversion because a locally valid fragment can still be incorrect in its parent context.
Implementation notes
- The first child is the numerator and the second is the denominator.
Accessibility and testing
- Keep a meaningful DOM structure instead of replacing the expression with an image.
- Test keyboard selection, screen-reader output, browser rendering, and conversion back to LaTeX.
- Check that fallbacks do not expose raw tags or omit the mathematical relationship represented by <mfrac>.