# a1 vs AC

> English confusable word pair

## The two words

### a1
*adjective · frequency rank #12,173*
first rate or excellent

### AC
*noun · frequency rank #4,646*
Initialism of absolute ceiling.

## Source
Compiled from Wiktionary via kaikki.org (CC BY-SA). Data vintage: 2026-09-03.
Canonical page: https://plainspell.com/en/vs/a1-vs-ac