What does "protium" mean?

The lightest and most common isotope of hydrogen, having a single proton and no neutrons: ¹₁H. It is the only stable nuclide with no neutrons.

What is a synonym for "protium"?

Common synonyms include: deuterium, genus protium, hydrogen 1, hydrogen one, hydrogen-1, isobar.

//ˈpɹoʊ.tiəm// noun

noun ·Uncommon ·Advanced level

Noun

1
The lightest and most common isotope of hydrogen, having a single proton and no neutrons: ¹₁H. It is the only stable nuclide with no neutrons.
"So far there are no differences among the protiums extracted at various labs, except for concentration levels."
2
An atom of this isotope.
"This radioactive decay leaves behind a protium as well."

"So far there are no differences among the protiums extracted at various labs, except for concentration levels."

From proto- + -ium. From Ancient Greek πρῶτος (prôtos, “first”).

Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.