Functional gastrointestinal disorders (FGID), also known as disorders of gut–brain interaction, include a number of separate idiopathic disorders which affect different parts of the gastrointestinal tract and involve visceral hypersensitivity and motility disturbances. Definition Using the Delphi method, the Rome Foundation and its board of directors, chairs and co-chairs of the ROME IV committees developed the current definition for disorders of gut-brain interaction. A group of disorders classified by GI symptoms related to any combination of: Motility disturbance Visceral hypersensitivity Altered mucosal and immune function Altered gut microbiota Altered central nervous system (CNS) processing Classification Terms such as functional colonic disease (or functional bowel disorder) refer in medicine to a group of bowel disorders which are characterized by chronic abdominal complaints without a structural or biochemical cause that could explain symptoms. Other functional disorders relate to other aspects of the process of digestion. The consensus review process of meetings and publications organised by the Rome Foundation, known as the Rome process, has helped to define the functional gastrointestinal disorders. Successively, the Rome I, Rome II, Rome III and Rome IV proposed consensual classification system and terminology, as recommended by the Rome Coordinating Committee. These now include classifications appropriate for adults, children and neonates/toddlers. The current ROME IV classification, published in 2016, is as follows: A. Esophageal disorders A1. Functional chest pain A2. Functional heartburn A3. Reflux hypersensitivity A4. Globus A5. Functional dysphagia B. Gastroduodenal disorders B1. Functional dyspepsia B1a. Postprandial distress syndrome (PDS) B1b. Epigastric pain syndrome (EPS) B2. Belching disorders B2a. Excessive supragastric belching B2b. Excessive gastric belching B3. Nausea and vomiting disorders B3a. Chronic nausea vomiting syndrome (CNVS) B3b. Cyclic vomiting syndrome (CVS) B3c. Cannabinoid hyperemesis syndrome (CHS) B4. Rumination syndrome C. Bowel disorders C1. Irritable bowel syndrome (IBS) IBS with predominant constipation (IBS-C) IBS with predominant diarrhea (IBS-D) IBS with mixed bowel habits (IBS-M) IBS unclassified (IBS-U) C2. Functional constipation C3. Functional diarrhea C4. Functional abdominal bloating/distension C5. Unspecified functional bowel disorder C6. Opioid-induced constipation D. Centrally mediated disorders of gastrointestinal pain D1. Centrally mediated abdominal pain syndrome (CAPS) D2. Narcotic bowel syndrome (NBS)/ Opioid-induced GI hyperalgesia E. Gallbladder and sphincter of Oddi disorders E1. Biliary pain E1a. Functional gallbladder disorder E1b. Functional biliary sphincter of Oddi disorder E2. Functional pancreatic sphincter of Oddi disorder F. Anorectal disorders F1. Fecal incontinence F2. Functional anorectal pain F2a. Levator ani syndrome F2b. Unspecified functional anorectal pain F2c. Proctalgia fugax