MathML Fundamentals - Identifier mi

An mi element represents a symbolic name or arbitrary text that should be rendered as an identifier. Identifiers can include variables, function names, and symbolic constants. MathML Fundamentals

xx + x + x + y + z + w + x

MathML

<math>
    <mi>xx</mi>
    <mo>+</mo>
    <mi>x</mi>
    <mo>+</mo>
    <mi mathvariant="bold">x</mi>
    <mo>+</mo>
    <mi mathcolor="#ff0000">y</mi>
    <mo>+</mo>
    <mi mathcolor="blue">z</mi>
    <mo>+</mo>
    <mi mathbackground="#ff8844">w</mi>
    <mo>+</mo>
    <mi mathbackground="blue">x</mi>
</math>