Acid indigestion 
See "acid reflux."

Acid reflux
The process of stomach acid (gastric juices that help digest food) and other fluids backing up from the stomach into the esophagus. Also known as acid indigestion gastroesophageal reflux, and popularly, as heartburn.

Antacids
Antacids are medicines designed to eliminate the symptoms of acid indigestion (heartburn) by neutralizing the stomach acid that causes them. They are usually over-the-counter products, that is, they are available without a prescription. 

Barrett's esophagus
A complication of severe chronic GERD in which cells in the lining of the esophagus become abnormal in color and shape (probably because of being irritated by the stomach acid and fluids that back up into the esophagus). These cells may undergo further changes that make them precancerous.

Biopsy
A biopsy is the removal of a sample of tissue so it can be examined for damage, infection, abnormal growths, genetic analysis, etc. to help make a diagnosis.

EGD (Esophagogastroduodenoscopy)
Often called an upper endoscopy, this is a medical test in which a thin, flexible, plastic tube with a tiny camera and light at the end (an endoscope) is slid down the esophagus and perhaps into the stomach, so its inner surfaces can be seen and examined.

Esophageal
Having to do with the esophagus.

Esophagitis
Esophagitis is a condition in which the esophagus is irritated and inflamed (red and swollen), usually caused by the stomach acids that flow up into the esophagus because of GERD.

Esophagram
An esophagram is another name for a barium x-ray (also known as a barium swallow radiograph) of the esophagus. For a barium x-ray, the person drinks a chalky fluid that enables the x-ray camera to produce better images.

Esophagus
The esophagus (also called the gullet) is the tube that connects the throat to the stomach. When you swallow, the muscles in the walls of the esophagus contract and push whatever is in it down, toward the stomach.

Fundoplication (anti-reflux surgery)
A surgical treatment for GERD in which the upper part of the stomach is wrapped around the LES to strengthen it and repair any hiatal hernia.

Gastroesophageal
Having to do with both the stomach and the esophagus.

Gastroesophageal reflux (GER)
See "acid reflux."

Gastroesophageal reflux disease(GERD)
A condition in which GER (acid reflux) happens frequently, which can (but not necessarily) lead to esophagitis, stricture, Barrett's esophagus, and other conditions.

H2 blockers (also called H2-receptor antagonists) 
H2 blockers are drugs that reduce the production of stomach acid and therefore reduce or eliminate the symptoms of acid reflux and GERD.

Heartburn
The popular term for the painful or burning sensation in the center of the chest, behind the breastbone, that is the usual result of acid reflux, the process of acid and fluids from the stomach backing up into the esophagus.

Hiatal hernia
A condition in which the upper part of the stomach and the LES protrude into the chest by pressing against the diaphragm. This can weaken those muscles, increasing the chance of acid reflux.

Laparoscopy
Laparoscopy is type of minimally invasive surgery in which tiny incisions are made, through which tiny instruments with attached mini-cameras are inserted; the surgeon can then manipulate the instruments while watching a video monitor.

Lower esophageal sphincter (LES)
The LES is a band of muscle that runs around the bottom of the esophagus, where it enters the stomach. Normally, the LES contracts so that food and fluids in the stomach can't flow back into the esophagus.

Over-the-counter (OTC)
medicine Over-the-counter medicines are drugs that can be bought without a prescription. Most popular, heavily advertised antacids are over-the-counter products.

Precancerous
Precancerous cells are at greater risk of becoming cancer cells. However, precancerous cells do not necessarily become cancer cells.

Proton pump inhibitors (PPIs)
PPIs are drugs that reduce the production of stomach acids (gastric juices) thereby eliminating the symptoms of GERD. They do the same thing as H2 blockers but are generally thought to be stronger and more effective.

Reflux
Reflux is the process of stomach acid (gastric juices that help digest food) and other fluids flowing back from the stomach up into the esophagus. The result is heartburn.  Known more accurately as "acid reflux" or "gastroesophageal reflux."

Stricture
When speaking of the esophagus, stricture refers to a narrowing within it.