quadrium

== English == === Etymology 1 === ==== Noun ==== quadrium (uncountable) (education) Synonym of quadrivium. === Etymology 2 === From quadr- +‎ -ium. ==== Noun ==== quadrium (uncountable) (physics, rare) A highly unstable synthetic isotope of the element hydrogen, 41H, having one proton and three neutrons. Alternative form: Q (deprecated symbol) Synonyms: H-4, ⁴H, hydrogen-4, hydrogen 4 Hypernyms: hydrogen, H Coordinate terms: protium, H-1, ¹H, hydrogen-1, hydrogen 1, normal hydrogen, light hydrogen (1 nucleon); H-2, ²H, D, hydrogen-2, hydrogen 2, heavy hydrogen (2 nucleons); H-3, ³H, T, tritium, hydrogen-3, hydrogen 3 (3 nucleons); hyperhydrogen (physics, rare) A quadrium atom or nucleus.