Which to use
“sth” is a pronoun and “STI” is a noun - they look or sound alike but fill different roles in a sentence.
- #40,035
- “sth” frequency rank
- #26,266
- “STI” frequency rank
- 66301
- confusion score
Side-by-Side Comparison
| Feature | sth | STI |
|---|---|---|
| Definition | Abbreviation of something. | Initialism of sexually transmitted infection (also S.T.I.). |
Letter map: sth vs STI
Shared letters muted; letters that set sth and STI apart highlighted. Shared run: 2.
Role in the sentence - sth and STI
Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: sth is apronoun and STIanoun. On the page they differ by a single letter - h in “sth” becomes i in “STI”. Our composite confusion score for this pair is 66301, derived from the frequency rank of both members and their visual similarity.
sth is recorded at frequency rank #40,035, classified as apron. STI is at rank #26,266, tagged as anoun.
Glosses for this pair are partially populated in our dataset, but the full side-by-side definitions above should still guide you to the right choice.
With a confusion score of 66301, this pair ranks #68,648 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of sth vs STI
Shared letters: st. Private to "sth": h. Private to "STI": i.
"sth" · 3 letters · shape CCC · "STI" · 3 letters · shape CCV
Frequently Asked Questions
Is swapping "sth" for "STI" ever safe?
Which is more common, "sth" or "STI"?
Useful next steps
Pair "sth" vs "STI" is on the table, pick a follow-up below.
- Full dictionary entry for "sth" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "STI" - compare definitions side by side with the headword page. Word entry
- This pair ranks #68,648 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "sth" and "STI" also get mixed up with nearby pairs, the highest-scored neighbour is "Sif vs sth". Nearby pair
Confusion rank #68,648 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.