lactic acid

American  

noun

Biochemistry.

1. a colorless or yellowish, syrupy, water-soluble liquid, C 3 H 6 O 3 , produced during muscle contraction as a product of anaerobic glucose metabolism, abundant in sour milk, prepared usually by fermentation of cornstarch, molasses, potatoes, etc., or synthesized: used chiefly in dyeing and textile printing, as a flavoring agent in food, and in medicine.

---

lactic acid British  

noun

1. Systematic name: 2-hydroxypropanoic acid.  a colourless syrupy carboxylic acid found in sour milk and many fruits and used as a preservative ( E270 ) for foodstuffs, such as soft margarine, and for making pharmaceuticals and adhesives. Formula: CH 3 CH(OH)COOH

---

lactic acid Scientific  

/ lăk′tĭk /

1. A syrupy, water-soluble organic acid produced when milk sours or certain fruits ferment. It is also produced in the body during the anaerobic metabolism of glucose, as in muscle tissue during exercise, where its buildup can cause cramping pains. A synthetic form of lactic acid is used as a flavoring and preservative, in dyeing and textile printing, and in pharmaceuticals. Chemical formula: C ₃ H ₆ O ₃ .

---

Etymology

Origin of lactic acid

First recorded in 1780–90

Example Sentences

“You’ve got lactic acid up to your eyeballs,” Porino said.

From The Wall Street Journal • Feb. 6, 2026

The researchers used direct acidification in their experiments, adding lactic acid to H5N1-spiked milk to produce cheeses with varying levels of acidity for testing.

From Science Daily • Oct. 21, 2025

“Whether it’s lactic acid building up, anxiety or excitement, I’ve seen it for years.”

From Los Angeles Times • Aug. 23, 2025

As a zit-faced grad student, I started a new research project that used lactic acid bacteria, or LAB, as a method for food safety.

From Slate • Feb. 22, 2025

My entire body aches, especially my legs, which burn with lactic acid even when I am not moving.

From "Insurgent" by Veronica Roth