Once your business management system has been independently audited by a Registrar, who has confirmed that it complies with the requirements of ISO 9001:2000 or ISO 14001, with the issuance of a certificate, is your system now considered "Certified" or "Registered"?
A look at the definitions in ISO/IEC Guide 2 and ISO/IEC DIS 17000 reveal slightly different meanings:
Certification: refers to the issuing of written assurance (the certificate) by an independent, external body that has audited an organization's management system and verified that it conforms to the requirements specified in the standard.
Registration: means that the auditing body then records the certification in its client register.
Given these definitions, your business management system has been both "Certified" and "Registered". For practical purposes, the use of either term is acceptable and can be used interchangeably.