lye

American  

[lahy] / laɪ /

noun

Chemistry.

1. a highly concentrated, aqueous solution of potassium hydroxide or sodium hydroxide.

2. any solution resulting from leaching, percolation, or the like.

---

lye British  

/ laɪ /

noun

1. any solution obtained by leaching, such as the caustic solution obtained by leaching wood ash

2. a concentrated solution of sodium hydroxide or potassium hydroxide

---

lye Scientific  

/ lī /

1. A strong alkaline solution or solid of potassium hydroxide or sodium hydroxide, made by allowing water to wash through wood ashes. It is used to make soap and drain and oven cleaners. Chemical formula: KOH or NaOH.

---

Etymology

Origin of lye

First recorded before 900; Middle English lie, ley, Old English lēag; cognate with Dutch loog, German Lauge “lye,” Old Norse laug “warm bath”; see lave ¹

Explanation

Lye is an alkaline solution that's used for cleaning. If you were a maid about 200 years ago, you probably cleaned the chamber pots with lye. Lye is an old cleaning product and an old word too. It comes from the Old English léag, which is related to the root for "wash" in our word lather. Lye is still used to make soap, but you probably won't come across the word except in old novels. If you become a historical re-enactor, say goodbye to body wash and hello to lye.

Example Sentences

The prohibition against soap comes from a time when all soap was made with lye, which could eat through a patina in minutes.

From Seattle Times • Apr. 13, 2024

The operator watched as the intruder clicked into various software programs before landing on a function that controls the amount of sodium hydroxide, or lye, in the plant’s water system.

From Los Angeles Times • May 8, 2023

In 2014, Caldeira and colleagues added sodium hydroxide—also known as lye and an ingredient in many soaps and detergents—to a part of Australia’s Great Barrier Reef.

From Science Magazine • Dec. 15, 2022

It was sodium hydroxide, the chemical in lye.

From New York Times • Aug. 18, 2022

And though she might have to have these sheets burned in the morning, and possibly have to bathe in lye herself, it was nice to have a friend.

From "Bone Gap" by Laura Ruby