Acid Reflux: A disorder in which acid in the stomach comes up into the oesophagus, because the valve separating the stomach and oesophagus does not function properly.

Heartburn: Pain due to regurgitation (reflux) of juices from the stomach into the oesophagus; pyrosis.

Achalasia cardia: Achalasia cardia is a condition where the esophageal peristaltic movements in the lower part of the esophagus are absent and the tone of the lower esophageal sphincter is increased.