# ppm vs psi

> English confusable word pair

## The two words

### ppm
*noun · frequency rank #23,949*
Initialism of parts per million (10000 ppm = 1%).

### psi
*noun · IPA /psaɪ/ · frequency rank #16,099*
The twenty-third letter of Classical and Modern Greek and the twenty-fifth letter of Old and Ancient Greek.

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