Multitenancy refers to a principle in software architecture where a single instance of the software runs on a server, serving multiple client organizations (tenants). Multitenancy is contrasted with a multi-instance architecture where separate software instances (or hardware systems) are set up for different client organizations. With a multitenant architecture, a software application is designed to virtually partition its data and configuration so that each client organization works with a customized virtual application instance. (from http://en.wikipedia.org/wiki/Multitenancy).
In ELIS, Multitenancy is achieved by assigning users different roles in the Curriculum Management system.