The NIPR adopted the definition of the Institute of Public Relations UK now Chartered Institute of Public Relations UK in 1978 and its  defined thus: "Public Relations is the deliberate, planned and sustained effort aimed at establishing and maintaining goodwill and mutual understanding between an organization and its publics"

The Mexican Statement

The World Assembly of Public Relations Associations gave its own definition of Public Relations
in Mexico in August 1978.

It said, "Public Relations is the Art and Social Science of analyzing trends, predicting their consequences, counseling organization's leaders and implementing planned programs of action that will serve both the organization and the public interests. 
A distinctive management function which helps establish and maintain mutual lines of communication; understanding, acceptance and co-operation between an organization and its publics; involves the management of problems or issues; helps management to keep informed responsive to public opinion; defines and emphasizes the responsibility of management to keep abreast of and effectively utilize change, serving as an early warning system to help anticipate trends; and uses research and sound and ethical communication techniques as its principal tools - Dr. Rex F. Harlon  1976
Public Relations is a combination of philosophy, sociology, economics, language, psychology, journalism, communication and other knowledge into a system of human understanding - Herbert M. Baus 
Persuasive communications to ensure that an organization gets the reputation it deserves, and guiding its behavior to help it deserve a good reputation - Warren Newman
Public Relations is the attempt by information, persuasion and adjustment to engineer public support for a cause or institution - Edward Bernays