# Haldane's rule

> English word · Proper noun

## Definitions
1. An observation about the early stage of speciation, stating that if in a species hybrid only one sex is inviable or sterile, that sex is more likely to be the heterogametic sex.

## Etymology
Formulated in 1922 by the British evolutionary biologist J. B. S. Haldane.

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