# Banach-Tarski paradox

> English word · Proper noun

## Definitions
1. A theorem in set-theoretic geometry, which states that given a solid ball in three‑dimensional space, there exists a decomposition of the ball into a finite number of disjoint subsets, which can then be put back together in a different way to yield two identical copies of the original ball.

## Etymology
Named after Polish mathematicians Stefan Banach and Alfred Tarski.

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