active mass

noun

1

: the concentration of a reacting substance expressed usually in moles per liter

2

: the concentration of the portion of a dissolved electrolyte that is dissociated into ions and hence is capable of carrying the electric current

Word History

First Known Use

1879, in the meaning defined at sense 1

The Ultimate Dictionary Awaits

Expand your vocabulary and dive deeper into language with Merriam-Webster Unabridged.

1. Expanded definitions
2. Detailed etymologies
3. Advanced search tools
4. All ad-free

Discover what makes Merriam-Webster Unabridged the essential choice for true word lovers.

Start Your Free Trial Now