Post Infectious IBS is a subtype of irritable bowel syndrome (IBS) that begins after an episode of infectious gastroenteritis. It describes ongoing bowel symptoms such as abdominal pain and altered stool pattern after the acute infection has resolved. It is most commonly used in outpatient gastroenterology and primary care to frame a specific clinical history of “IBS after a gut infection.” It is a clinical diagnosis based on symptoms and context rather than a single definitive test.

Functional Constipation is a diagnosis used when constipation symptoms are present without an identifiable structural, metabolic, or medication-related cause. It is defined using symptom-based criteria, most commonly the Rome IV criteria, rather than a single lab test or imaging finding. Clinicians use it in outpatient gastroenterology and primary care to describe chronic constipation patterns and guide evaluation. It is also used in research and clinical documentation to standardize how constipation is described across patients.

Functional Dyspepsia is chronic or recurrent upper abdominal discomfort without an identifiable structural cause on routine evaluation. It is commonly used as a clinical diagnosis in gastroenterology when symptoms suggest stomach or duodenal disease but tests are unrevealing. In plain terms, it describes “indigestion” symptoms that persist even when no ulcer, cancer, or obvious inflammation is found. It is discussed in clinics, endoscopy units, and primary care because it is a frequent reason for upper gastrointestinal (GI) symptom evaluation.

Visceral Hypersensitivity means the internal organs feel pain or discomfort more easily than expected. It describes heightened sensing from the gastrointestinal (GI) tract or other abdominal organs. It is commonly discussed in functional GI disorders, such as irritable bowel syndrome (IBS). Clinicians also use it to interpret symptoms when tests do not show clear structural disease.

Leaky Gut is a nontechnical term that usually refers to increased intestinal permeability. It describes a situation where the gut lining allows more substances to pass from the intestinal lumen into the body than expected. The phrase is common in popular health discussions and also appears in research contexts. In clinical practice, clinicians more often use precise terms like “intestinal barrier dysfunction” rather than Leaky Gut.

Intestinal Permeability describes how easily substances pass from the gut lumen into the body across the intestinal lining. It is a normal physiologic property that supports nutrient and water absorption while limiting harmful exposures. In clinical medicine, the term is commonly used when discussing barrier function, inflammation, infection, and certain GI disorders. It may also refer to how permeability is *measured* in research or selected clinical settings.

The Gut Barrier is the body’s multi-layer system that separates the intestinal lumen from the internal bloodstream and tissues. It allows nutrient and water absorption while limiting entry of pathogens and toxins. It is discussed in gastroenterology, hepatology, critical care, and nutrition science. Clinicians reference it when thinking about inflammation, infection risk, and intestinal permeability.

Gut Flora is the community of microorganisms that live in the gastrointestinal (GI) tract. It mainly refers to bacteria, but also includes viruses, fungi, and archaea. The term is commonly used in gastroenterology to describe how microbes interact with digestion and immunity. It is also used in clinical discussions about infections, inflammation, and “microbiome” testing.

The Microbiome is the community of microbes that live on and inside the human body. It includes bacteria, viruses, fungi, and other microorganisms, plus their genes and byproducts. In gastroenterology, the term most often refers to the gut Microbiome in the intestines. It is commonly used in clinical research and increasingly in patient-centered discussions of digestive health.

Fecal Transplant is a therapy that transfers processed stool from a screened donor into a patient’s gastrointestinal tract. It aims to restore a healthier community of gut microbes (the intestinal microbiome). It is most commonly discussed in the care of recurrent *Clostridioides difficile* infection (often abbreviated *C. difficile* or CDI). It is performed in specialized clinical settings using standardized screening and delivery methods.