# alum vs AUC

> English confusable word pair

## The two words

### alum
*noun · IPA /ˈæl.əm/ · frequency rank #20,832*
An astringent salt, usually occurring in the form of pale crystals, much used in the dyeing and tanning trade and in certain medicines, and now understood to be a double sulphate of potassium and aluminium (K₂SO₄·Al₂(SO₄)₃·24H₂O).

### AUC
*adverb · frequency rank #48,600*
According to the Roman era, which reckons the number of years passed from the foundation of the city of Rome by Romulus, now usually taken as 753 bc.

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