What does reflux mean?
Reflux means a backward flow. Its most familiar use is medical: reflux commonly describes the movement of stomach acid and other gastric contents upward into the esophagus, where it may cause heartburn, irritation, or inflammation. The condition is often called acid reflux or gastroesophageal reflux disease when symptoms are persistent. Reflux can also refer more generally to any liquid that flows back toward its source. In chemistry, reflux is the deliberate heating of a liquid so that its vapour rises into a condenser, becomes liquid again, and returns to the reaction vessel; this allows a reaction to continue at a high temperature without losing volatile material. The term is technical but broadly understood in relevant professional settings. Its defining idea is reversal: a flow that normally proceeds in one direction turns back upon itself.
The backward flow of a liquid, especially stomach acid from the stomach into the esophagus; in chemistry, the return of condensed vapour to a heated vessel.
"The test was repeated after the medication reduced her reflux."
The medical sense is the most common in everyday use. The chemical sense is standard in laboratory and industrial contexts.
To flow back, especially for stomach contents to move upward into the esophagus or for condensed vapour to return to a heated vessel.
"Acid may reflux into the esophagus after a large meal."
The verb is less common than the noun and is most often encountered in medical or technical descriptions.
Used for distinct episodes or instances of backward flow.
"The recording showed three separate refluxes during the night."
Acid reflux is not stomach acid flowing into the stomach—it is stomach acid flowing back the wrong way into the esophagus.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does reflux come from?
Reflux comes from Latin refluere, meaning “to flow back,” formed from re-, meaning “back” or “again,” and fluere, “to flow.” The Latin past participle refluxus helped form the English noun, which has been in use since the early modern period. English words such as flux, fluent, confluence, and effluence belong to the same broad Latin family associated with flowing.
Related word forms
How reflux is actually used
In medicine, reflux is standard in both British and American English and is especially associated with gastroesophageal reflux. In laboratory contexts, it is a technical term for the controlled return of condensed vapour to the reaction vessel.
Easily confused with reflux
Reflux usually means a backward flow of fluid, whereas regurgitation more specifically means bringing swallowed material back into the mouth.