What is the difference between registration, certification and accreditation?

The assessment of an environmental management system against the requirements of the ISO14001 standards and the subsequent issuing of a certificate to confirm that it is in conformance with the standard’s requirements is variously referred to in different countries as certification or registration.
Accreditation is another term which, in the ISO14001 context, is also sometimes used – wrongly – as a synonym for "certification" or "registration". "Accreditation" is the procedure by which an authoritative body gives formal recognition that a body or person is competent to carry out specific tasks. In the ISO14000 context, it relates to the work of national accreditation bodies which have been set up in a number of countries to provide some measure of control over the activities of quality system or environmental management system certification bodies. An accreditation body will accredit – or, in simpler language, approve – a certification body as competent to carry out ISO 14000 certification of environmental management systems, in specified business sectors.