Knowledge representation and reasoning are important component in knowledge engineering. In most information systems knowledge capture and then processed using different method like classified and compute...etc. One of the methods for a processing knowledge is Ontology. Ontology is an organized means of representing the knowledge detailed to the domain of interest. This survey focused to get a clear understanding of what Ontology? . And how to building Ontology in various domains Like intelligent system –E- learning – software engineering and discuss new approaches for ontology in a various domains in knowledge representations. And tools that used in building ontology for example, (UML) Unified Modeling Language this is an associated languages to build ontology.