The language around gut-brain health is dense, and a lot of it gets used loosely. Here are the terms that actually matter, each defined the way I would explain it to a patient across the desk.
Disorders of gut-brain interaction (DGBI)
Disorders of gut-brain interaction (DGBI) are conditions in which the gut and the brain do not communicate normally, producing real symptoms such as pain, nausea, bloating, or changed bowel habits without visible damage on routine tests. This is the current medical term. It replaced the older label "functional GI disorders," which wrongly implied the symptoms were imaginary.
The gut-brain axis
The gut-brain axis is the constant two-way communication between your digestive system and your brain. They talk through nerves, hormones, immune signals, and chemicals made by gut bacteria. Because the line runs both directions, stress can change digestion and gut trouble can affect mood, sleep, and how strongly you feel pain.
The vagus nerve
The vagus nerve is the main physical cable of the gut-brain axis. It runs from the brainstem down through the chest and into the abdomen, carrying signals in both directions. Most of its traffic is actually gut-to-brain, which is one reason the digestive tract has such a strong influence on how you feel overall.
Visceral hypersensitivity
Visceral hypersensitivity means the nerves of the internal organs are turned up too high, so normal digestion gets read as pain or discomfort. A degree of stretching or gas that most people never notice can feel sharp or intense. It is a central feature of many DGBI, and it explains symptoms that normal test results cannot.
Central sensitization
Central sensitization is when the spinal cord and brain amplify pain signals, so the whole nervous system becomes more reactive over time. Ordinary sensations get magnified, and pain can persist after any initial trigger is gone. It often shows up alongside conditions like migraine, fibromyalgia, and irritable bowel syndrome, which tend to travel together.
Nociplastic pain
Nociplastic pain is a third category of pain, separate from injury pain and nerve-damage pain. It comes from a nervous system that processes pain abnormally, without ongoing tissue damage to explain it. Much of the discomfort in DGBI fits here, which is why scans and scopes can look clean while the pain is entirely real.
Gut motility
Gut motility is the coordinated muscle movement that pushes food, fluid, and gas through the digestive tract. When it runs too fast, too slow, or out of rhythm, the result can be diarrhea, constipation, bloating, or a sense of fullness. Many gut-brain conditions involve motility that has fallen out of its normal pattern.
Intestinal permeability
Intestinal permeability describes how tightly the gut lining controls what passes from the digestive tract into the bloodstream. When the barrier loosens, more particles can cross than usual, which may contribute to inflammation and symptoms. The popular name for this is "leaky gut," but intestinal permeability is the accurate term and the one worth learning.
The gut microbiome
The gut microbiome is the community of trillions of bacteria, viruses, and fungi living in your digestive tract. In a healthy state they help digest food, make certain vitamins, train the immune system, and produce chemicals that reach the brain. Shifts in this community are linked to many gut-brain conditions, though cause and effect are still being sorted out.
The HPA axis (hypothalamic-pituitary-adrenal axis)
The HPA axis (hypothalamic-pituitary-adrenal axis) is the body's central stress-response system. When you face a threat, the brain signals the adrenal glands to release cortisol and other stress hormones. This system is closely wired to the gut, which is why chronic stress can worsen digestive symptoms and why gut trouble can raise your overall stress load.
Irritable bowel syndrome (IBS)
Irritable bowel syndrome (IBS) is a common DGBI marked by recurring abdominal pain tied to bowel movements, along with changes in how often you go or how the stool looks. It is diagnosed by symptom pattern, not by a single test. Diet often plays a role, and the low-FODMAP approach is one evidence-based strategy people use to manage it.
Functional dyspepsia (FD)
Functional dyspepsia (FD) is persistent discomfort centered in the upper abdomen, including fullness soon after starting a meal, uncomfortable fullness afterward, or a burning sensation, without an ulcer or other structural cause on testing. It is one of the most common gut-brain conditions. You can read more in my deeper piece on functional dyspepsia.
Cyclic vomiting syndrome (CVS)
Cyclic vomiting syndrome (CVS) is a condition of repeated, stereotyped episodes of intense nausea and vomiting separated by stretches of feeling completely well. The attacks tend to follow a predictable pattern for a given person and often have identifiable triggers. Between episodes there is no ongoing sickness, which is a defining feature of the diagnosis.
Cannabinoid hyperemesis syndrome (CHS)
Cannabinoid hyperemesis syndrome (CHS) is a pattern of severe, cyclic nausea and vomiting linked to long-term, frequent cannabis use, often eased temporarily by hot showers or baths. It can be difficult to recognize because cannabis is widely used to treat nausea. I cover the evidence in detail in my article on cannabinoid hyperemesis syndrome.
FODMAPs
FODMAPs are a group of short-chain carbohydrates (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) that are poorly absorbed in some people. They draw water into the gut and get fermented by bacteria, producing gas, which can trigger bloating, pain, and altered bowel habits in sensitive individuals, especially those with irritable bowel syndrome.
Postprandial
Postprandial simply means "after eating." Clinicians use it to describe symptoms that appear once a meal is underway or shortly afterward, such as fullness, bloating, pain, or nausea. It is a useful word in gut-brain conditions because the timing of symptoms relative to meals is often a key clue to what is happening.
Rome criteria / Rome V
The Rome criteria are the international framework that defines and diagnoses disorders of gut-brain interaction based on specific symptom patterns rather than lab or imaging findings. Rome V is the current edition, updated by a global panel of experts. It is the standard that clinicians and researchers use to name these conditions consistently around the world.
How to use this
These are not vague labels or catch-all excuses. They describe real, common, well-studied conditions that affect a large share of people at some point in their lives, and understanding the vocabulary makes it far easier to follow your own care and ask better questions. This glossary is educational and is not a substitute for evaluation. If digestive symptoms are disrupting your daily life, sleep, or work, talk with a clinician who can assess you directly.
Knowing the right words is a small thing, but it changes how you advocate for yourself.