Faye Glenn Abdellah was an influential American nursing theorist and public health scientist. She developed a theory that identified 21 common nursing problems experienced by patients. These problems focused on maintaining physiological needs, sustaining care needs, remedial care needs, and restorative care needs. Abdellah's theory transformed nursing from a disease-centered focus to a patient-centered approach and helped establish nursing diagnosis as a formal step in the nursing process. Her work has significantly influenced nursing education, practice, and research.