MathML Fundamentals - Underscript-overscript Pair munderover

The munderover element attaches accents or limits placed both over and under a base. It always sets displaystyle to "false" within underscript and overscript, but increments scriptlevel by 1 only when accentunder or accent, respectively, are "false". Within base, it always leaves both attributes unchanged. MathML Fundamentals

Underscript, Overscript munderover Left to Right X maps to maps to Y X maps to maps to maps to maps to Y n = 1 + n = 1 + n = 1 + n = 1 + n = 1 x + y + z x + y + z Right to Left X maps to maps to Y X maps to maps to maps to maps to Y n = 1 + n = 1 + n = 1 + n = 1 + n = 1 x + y + z x + y + z

MathML

<math mathsize="80">
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mtext style="border:1px;" mathsize="50">Underscript, Overscript munderover</mtext>
    
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mtext style="border:1px;" mathsize="30">Left to Right</mtext>
    
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow style="border:1px">
        <mi>X</mi>
        <munderover>
            <mo>→</mo>
            <mtext>maps to</mtext>
            <mtext>maps to</mtext>
        </munderover>
        <mi>Y</mi>
    </mrow>
    <mrow style="border:1px">
        <mi>X</mi>
        <munderover overspace="-50%">
            <mo>→</mo>
            <mtext>maps to maps to maps to</mtext>
            <mtext>maps to</mtext>
        </munderover>
        <mi>Y</mi>
    </mrow>
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow style="border:1px;">
        <munderover style="border:1px">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
        <mo style="border:1px">+</mo>
        <munderover style="border:1px" align="left">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
        <mo style="border:1px">+</mo>
        <munderover style="border:1px" align="right">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
		<mo style="border:1px">+</mo>
        <munderover style="border:1px" accentunder="true" accent="true">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
             <mo style="border:1px">∞</mo>
        </munderover>   
        <mo style="border:1px">+</mo>
        <mstyle displaystyle='false' >
       	 <munderover style="border:1px">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
             <mo style="border:1px">∞</mo>
        </munderover>     
       </mstyle>         
    </mrow>
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow style="border:1px;">
        <munderover style="border:1px;">
            <mrow style="border:1px">
                <mi>x</mi>
                <mo>+</mo>
                <mi>y</mi>
                <mo>+</mo>
                <mi>z</mi>
            </mrow>
            <mo style="border:1px">⏟</mo>
            <mo style="border:1px">⏞</mo>
        </munderover>
        <munderover underspace="-0.1em" overspace="-0.1em" style="border:1px;">
            <mrow style="border:1px;">
                <mi>x</mi>
                <mo>+</mo>
                <mi>y</mi>
                <mo>+</mo>
                <mi>z</mi>
            </mrow>
            <mo style="border:1px;">⏟</mo>
            <mo style="border:1px;">⏞</mo>
        </munderover>
    </mrow>
    
    
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mtext style="border:1px;" mathsize="30">Right to Left</mtext>
    
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow dir="rtl">
	    <mrow style="border:1px">
	        <mi>X</mi>
	        <munderover>
	            <mo>→</mo>
	            <mtext>maps to</mtext>
	            <mtext>maps to</mtext>
	        </munderover>
	        <mi>Y</mi>
	    </mrow>
	    <mrow style="border:1px">
	        <mi>X</mi>
	        <munderover overspace="-50%">
	            <mo>→</mo>
	            <mtext>maps to maps to maps to</mtext>
	            <mtext>maps to</mtext>
	        </munderover>
	        <mi>Y</mi>
	    </mrow>
	</mrow>
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow style="border:1px;" dir="rtl">
        <munderover style="border:1px">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
        <mo style="border:1px">+</mo>
        <munderover style="border:1px" align="left">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
        <mo style="border:1px">+</mo>
        <munderover style="border:1px" align="right">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
            <mo style="border:1px">∞</mo>
        </munderover>
		<mo style="border:1px">+</mo>
        <munderover style="border:1px" accentunder="true" accent="true">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
             <mo style="border:1px">∞</mo>
        </munderover>   
        <mo style="border:1px">+</mo>
        <mstyle displaystyle='false' >
       	 <munderover style="border:1px">
            <mo style="border:1px">∑</mo>
            <mrow style="border:1px">
                <mi>n</mi>
                <mo>=</mo>
                <mn>1</mn>
            </mrow>
             <mo style="border:1px">∞</mo>
        </munderover>     
       </mstyle>         
    </mrow>
    <mspace linebreak="newline" indentalign="center"></mspace>
    <mrow style="border:1px;" dir="rtl">
        <munderover style="border:1px;">
            <mrow style="border:1px">
                <mi>x</mi>
                <mo>+</mo>
                <mi>y</mi>
                <mo>+</mo>
                <mi>z</mi>
            </mrow>
            <mo style="border:1px">⏟</mo>
            <mo style="border:1px">⏞</mo>
        </munderover>
        <munderover underspace="-0.1em" overspace="-0.1em" style="border:1px;">
            <mrow style="border:1px;">
                <mi>x</mi>
                <mo>+</mo>
                <mi>y</mi>
                <mo>+</mo>
                <mi>z</mi>
            </mrow>
            <mo style="border:1px;">⏟</mo>
            <mo style="border:1px;">⏞</mo>
        </munderover>
    </mrow>
    
    
    
</math>