# iff vs ill

> English confusable word pair

## The two words

### iff
*conjunction · IPA /ɪf ən(d)ˈəʊn.li ɪf/ · frequency rank #45,443*
Abbreviation of if and only if.

### ill
*adjective · IPA /ɪl/ · frequency rank #1,946*
Evil; wicked (of people).

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