# A4 vs AU

> English confusable word pair

## The two words

### A4
*name · frequency rank #18,471*
A4 class, a class of steam locomotive used on the London and North Eastern Railway.

### AU
*noun · frequency rank #6,867*
Initialism of alopecia universalis.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-09-02.
Canonical page: https://plainspell.com/en/vs/a4-vs-au