What’s the difference between DESIGNATIONS and CERTIFICATIONS?

The National Association of Realtor’s Center for Realtor Development explains both education options as two different choices of credentials. The Merriam-Websters Online dictionary defines credentials as “1:something that gives a title to credit or confidence; also :qualification 3a the applicant with the best credentials  2. credentials plural :testimonials or certified documents showing that a person is entitled to credit or has a right to exercise