# mesothorium

> English word · Noun

## Definitions
1. Certain members of the decay chain of thorium, mainly isotopes of radium and actinium

## Etymology
From meso- + thorium. Probably so-called because these two isotopes (²²⁸Ra and ²²⁸Ac) are, in the decay chain, intermediate between normal thorium (²³²Th) and radiothorium (²²⁸Th).

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-05-06.
Canonical page: https://plainspell.com/en/word/mesothorium