# SPF vs SST

> English confusable word pair

## The two words

### SPF
*noun · frequency rank #30,978*
Initialism of sun protection factor.

### SST
*noun · frequency rank #43,385*
Initialism of supersonic transport.

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