# leucine

> English word · Noun · IPA /ˈluː.siːn/ · frequency rank #57,517

## Definitions
1. An essential amino acid, C₆H₁₃NO₂, isomeric with isoleucine, found in most animal proteins; it is essential for growth in children.

## Etymology
Derived from Ancient Greek λευκός (leukós, “white”) + -ine, equivalent to leuco- + -ine.

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