STI vs su, What's the Difference?

Which to use

“STI” and “su” are a confusable English pair: similar on the page, but distinct in meaning, check the gloss before you choose.

#26,266
“STI” frequency rank: #8,094
“su” frequency rank: 34360
confusion score

Side-by-Side Comparison

Feature	STI	su
Definition	Initialism of sexually transmitted infection (also S.T.I.).	Alternative form of xu (“former Vietnamese currency”).

Letter map: STI vs su

Shared letters muted; letters that set STI and su apart highlighted. Shared run: 1.

3 ch

STI

2 ch

Pair insight - STI / su

STI and su are indexed as a confusable English pair. We have no recorded pronunciation or part of speech for both members, so the spelling overlap is what we can show you: they differ by 1 letter(s) in length. Our composite confusion score for this pair is 34360, derived from the frequency rank of both members and their visual similarity.

STI is recorded at frequency rank #26,266, classified as anoun. su is at rank #8,094, 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 34360, this pair ranks #321,523 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of STI vs su

Shared letters: s. Private to "STI": it. Private to "su": u.

"STI" · 3 letters · shape CCV · "su" · 2 letters · shape CV

Frequently Asked Questions

Can "STI" and "su" be used interchangeably?

No. They differ by 1 letter(s) in length, but the dictionary glosses above give them different meanings, so swapping one for the other changes what the sentence says.

Frequency check: "STI" vs "su" - which ranks higher?

"su" is the more common of the two: it sits at frequency rank #8,094 in our English list, against #26,266 for "STI". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

You've compared "STI" and "su". Here's where to go from here.

Full dictionary entry for "STI" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "su" - compare definitions side by side with the headword page. Word entry
This pair ranks #321,523 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"STI" and "su" also get mixed up with nearby pairs, the highest-scored neighbour is "Sif vs STI". Nearby pair

Confusion rank #321,523 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.