Overview

When authoring LaTeX, it is common to think exclusively about visual rendering. But math expressions are increasingly converted to MathML for web publication, and the structure of that MathML directly affects how accessible the equations are to screen reader users.

Guidance

The problem: structural ambiguity

Consider these two ways of writing a summation:

\sum_{i=1}^{n} a_i + b_i

\sum_{i=1}^{n} {a_i + b_i}

Both render identically. To a sighted reader, context and convention make the intended grouping clear. But without explicit braces, a LaTeX-to-MathML converter may not recognize that \(a_i + b_i\) is the summand (the thing being summed) rather than \(a_i\) alone with \(b_i\) added to the result afterward.

Why explicit structure matters for accessibility

MathML uses the <mrow> element to group expressions into logical units. When a LaTeX-to-MathML converter encounters explicit braces, it typically emits an <mrow> to hold the grouped content. This has two important consequences:

Structural navigation: Screen reader users can navigate equations structurally, not just linearly. An <mrow> surrounding a summand allows the user to move into it, hear it as a unit, and move out—analogous to how sighted readers visually parse an expression chunk-by-chunk.
Reduced ambiguity in speech: Without structural cues, a screen reader might announce the expression in a way that obscures the mathematical meaning. Explicit grouping helps the accessibility tool make better decisions about pausing, inflection, and description.

Recommended practice

For any large operator, wrap its operand in braces:

% Summation: group the summand
\sum_{{i=1}}^{{n}} {{a_i^2}}

% Product: group the multiplicand
\prod_{{k=1}}^{{n}} {{(x - r_k)}}

% Integral: group the integrand
\int_0^\infty {{e^{{-x^2}} \, dx}}

% Limit: group the expression
\lim_{{x \to 0}} {{\frac{{\sin x}}{{x}}}}

% Union and intersection
\bigcup_{{i \in I}} {{A_i \cap B_i}}

The visual output is unchanged, but the underlying MathML structure is now explicit and unambiguous for assistive technologies.

Back to Ten Tips for Accessible LaTeX Math Expressions

LaTeX Reference Guides (Canvas / MathJax 2.7)