noun ·Rare ·Advanced level

Definitions

Noun

1. 1
   The major stable isotope of argon, ⁴⁰₁₈Ar, having eighteen protons and twenty-two neutrons; it amounts to about 99.6% of the element in nature uncountable

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