Many professional designations in the United States take the form of post-nominal letters. Certifications are usually awarded by professional societies or educational institutes. Obtaining a certificate is voluntary in some fields, but in others, certification from a government-accredited agency may be legally required to perform certain jobs or tasks.
Organizations in the United States involved in setting standards for certification include the American National Standards Institute (ANSI) and the Institute for Credentialing Excellence (ICE). Many certification organizations are members of the Association of Test Publishers (ATP).

View More On Wikipedia.org