An abnormal change (metaplasia) in the cells of the inferior portion of the esophagus. The normal squamous epithelium lining of the esophagus is replaced by metaplastic columnar epithelium. Columnar epithelium refers to a cell type that is typically found in more distal parts of the gastrointestinal system. [https://orcid.org/0009-0006-4530-3154]