# Tonian

> English word · Adjective · IPA /ˈtəʊ.ni.ən/

## Definitions
1. Of a geologic period within the Neoproterozoic era from about 1000 to 850 million years ago.

## Etymology
From Ancient Greek τόνος (tónos, “stretch”).

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