# pionium

> English word · Noun

## Definitions
1. an exotic atom equivalent to a hydrogen atom with the proton replaced by a pion
2. an onium where the bound antiparticle-particle pair is a pion and an antipion.

## Etymology
From pion + -ium.

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