A new version of the ontology of professional mathematical knowledge OntoMathPRO is presented. This ontology is a conceptual model of the main branches of mathematics. The new version of the ontology introduces materialized relationships between concepts. To do this, ontology concepts are additionally divided into types and roles. Concepts-roles act as arguments of materialized relations. Also, one of the features of the new version of the ontology is the inclusion of multilingual lexicons for expressing mathematical concepts in natural language texts. The introduction of prerequisite relationships between ontology classes has expanded the possibilities of creating educational mathematical applications. Some important applications of the OntoMathPRO ontology in various fields of knowledge are indicated.