MathML
MathML is a XML-based markup language for writing Mathematics.
Presentation versus Content
MathML elements are dividing into MathML Presentation Elements and MathML Content Elements.
MathML in HTML
It is common to write MathML in HTML. For example:
<html>
<head>
<title>Example<title>
</head>
<body>
<p>
Here is some MathML in HTML:
</p>
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mfrac>
<mn>2</mn>
<mn>5</mn>
</mfrac>
</math>
</body>
</html>