# STI vs su

> English confusable word pair

## The two words

### STI
*noun · frequency rank #26,266*
Initialism of sexually transmitted infection (also S.T.I.).

### su
*noun · frequency rank #8,094*
Alternative form of xu (“former Vietnamese currency”).

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