This paper describes the use of ontologies in different aspects of software engineering. This use of ontologies varies from support for software developers at multiple sites to the use of an ontology to provide semantics in different categories of software, particularly on the Web. The world's first and only software engineering ontology and a project management ontology in conjunction with a domain ontology are used to provide support for software development that is taking place at multiple sites. Ontologies are used to provide semantics to deal with heterogeneity in the representation of multiple information sources, enable the selection and composition of web services and grid resources, provide the shared knowledge base for multiagent systems, provide semantics and structure for trust and reputation systems and privacy based systems and codification of shared knowledge within different domains in business, science, manufacturing, engineering and utilities. They, therefore, bring a new paradigm to software engineering through the use of semantics as a central mechanism which will revolutionize the way software is developed and consumed in the future leading to the development of software as a service bringing about the dawn of software engineering 2.0.