[proh-tee-uh m, -shee-uh m]

noun Chemistry.

the lightest and most common isotope of hydrogen. Symbol: H1

Origin of protium

First recorded in 1930–35; prot- + -ium Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for protium

Historical Examples of protium

  • I was prevented from doing this immediately by difficulties in the Protium Works.

  • We had supposed you would have been told when you were assigned to the protium research.

  • That is one reason I am so interested in this protium on which you chemists are working.

  • Nor did he possess any great knowledge of the protium mines, for he had never visited them.

  • I was immediately installed in my new office, as Director of the Protium Works.

British Dictionary definitions for protium



the most common isotope of hydrogen, having a mass number of 1

Word Origin for protium

C20: New Latin, from proto- + -ium
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

protium in Medicine


[prōtē-əm, prōshē-]


The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

protium in Science


[prōtē-əm, -shē-əm]

The most abundant isotope of hydrogen, having an atomic mass of 1. Its nucleus consists of a single proton. See more at hydrogen.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.