The mfenced element provides a convenient form in which to express common constructs involving fences (i.e. braces, brackets, and parentheses), possibly including separators (such as comma) between the arguments. MathML Fundamentals
<math mathsize="100">
<mspace linebreak="newline" indentalign="center"></mspace>
<mtext style="border:1px;">MFenced Test</mtext>
<mspace linebreak="newline" indentalign="center"></mspace>
<mfenced style="border:1px">
<mrow>
<mi>a</mi>
<mo>+</mo>
<mi>b</mi>
</mrow>
</mfenced>
<mspace linebreak="newline" indentalign="center"></mspace>
<mfenced style="border:1px">
<mfrac style="border:1px">
<mi>a</mi>
<mi>b</mi>
</mfrac>
<mo>+</mo>
<mi>c</mi>
</mfenced>
<mfenced style="border:1px" open="{" close="}">
<mfrac style="border:1px">
<mi>a</mi>
<mi>b</mi>
</mfrac>
<mi>b</mi>
<mi>c</mi>
</mfenced>
<mfenced style="border:1px" open="⌈" close="⌉" separators="|">
<mfrac style="border:1px">
<mi>a</mi>
<mi>b</mi>
</mfrac>
<mi>b</mi>
<mi>c</mi>
</mfenced>
<mspace linebreak="newline" indentalign="center"></mspace>
<mfenced style="border:1px" separators="|">
<mi>a</mi>
<mi>b</mi>
<mi>c</mi>
</mfenced>
<mspace linebreak="newline" indentalign="center"></mspace>
<mfenced style="border:1px" separators=",|">
<mi>a</mi>
<mi>b</mi>
<mi>c</mi>
<mi>d</mi>
<mi>e</mi>
</mfenced>
</math>