A survey has been presented on the usage of ontology in various domains like Medical, Agriculture, Geosciences, Education, Marine, Communication, Computer, Chemical, Defence, Linguistic etc. A summary of the available ontology developed in various domains is given and no attempt has been made to evaluate them. Only a broad picture of ontology applications in various domains practiced today are described. In some cases details like number of concepts, relationship, classes and subclasses defined are also given. The survey indicated that considerable effort has gone in the development of ontology in the domains of medical, education, computer science. It is noted that rather limited effort has gone into the development of ontology in the domains of power plants and atomic energy.