Plurimath

`phantom` (unary)

Phantom

LaTeX

\phantom{x}

MathML

<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
  <mstyle displaystyle="true">
    <mphantom>
      <mi>x</mi>
    </mphantom>
  </mstyle>
</math>

OMML

<m:oMathPara>
  <m:oMath>
    <m:phant>
      <m:phant>
        <m:show val="m:off"/>
      </m:phant>
      <m:e>
        <m:r>
          <m:t>x</m:t>
        </m:r>
      </m:e>
    </m:phant>
  </m:oMath>
</m:oMathPara>

UnicodeMath

⟡(x)
Note
In AsciiMath conversion, it will add `\ ` replacing all the letters as value of the object. For example, the output of this example in AsciiMath will be `\ `.