# light water

> English word · Noun

## Definitions
1. Any water molecules (H₂O) containing two protium (¹H, hydrogen-1) atoms.
2. Any water molecules (H₂O) containing two protium (¹H, hydrogen-1) atoms.
3. Foam formed by water and any of various additives, used in firefighting because it floats on flammable liquids lighter than water. (The additives were originally fluorocarbon surfactants but today are increasingly fluorine-free.)

## Etymology
By reference to atomic weight and atomic mass; more at light hydrogen.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/light-water