Unambiguous representation of mathematics is crucial for communications among humans or among computer systems. OpenMath is a standard aimed at supporting a semantically rich interchange of mathematics among varied computational software tools such as computer algebra systems, theorem provers, and tools for visualizing or editing mathematical text. MathML is a W3C Recommendation for the encoding of mathematics 'on the web' which also includes mechanisms for encoding mathematical semantics. We introduce each of these two languages and describe their relationships.