More than 225 major works published in English from national and international sources on andragogy are presented here, in order to provide a clear and understandable, international foundation for the linkage between the research, theory and practice of andragogy and its application to Adult Education and Human Resource Development. Six themes have emerged that provide a foundation for the linkage. The evolution of the term: historical antecedents shaping the concept; comparison of American and European understanding; popularizing and sustaining the American and world-wide concept; practical applications; and theory, research, and definition.