Ontology is a formal structured presentation of any number of concepts and their respective relationships to each other. The ontology describes the knowledge with help of standardized terminology, meaning of individual concepts and semantic relations between the terms. All information in ontology forms a kind of network for representing knowledge. This knowledge can be used in different ways, for example in informational retrieval, artificial intelligence, the Semantic Web, software engineering, biomedical informatics, library science, and so on.