# Hartogs number

> English word · Noun

## Definitions
1. For a given set X, the cardinality of the least ordinal number α such that there is no injection from α into X.

## Etymology
After German-Jewish mathematician Friedrich Hartogs (1874–1943).

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