heartburn

This term describes a specific physiological sensation rather than a cardiac event, despite the word heart. It is used primarily in medical and everyday health contexts to describe the symptom of acid reflux. Because it refers to a condition or a sensation, it is treated as an uncountable noun.

In clinical settings, it is often distinguished from GERD (Gastroesophageal Reflux Disease), where heartburn is the symptom and GERD is the chronic condition. It is almost always paired with descriptors of intensity, such as severe or mild, or frequency, such as chronic or occasional.