Heartburn, acid reflux, and acid indigestion are all terms used to describe a burning feeling in the chest or a backwash of stomach contents into the mouth or the esophagus (the tube that connects the throat to the stomach). 
 
If you have these symptoms more than twice a week for more than a few weeks, you may be diagnosed as having gastroesophageal reflux disease (GERD).

GERD is a chronic condition in which heartburn, acid reflux, and indigestion occur more than twice a week for more than a few weeks.

Paper

JAMA patient page. Gastroesophageal reflux disease.

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