STIvssumWhich spelling fits?

Which to use

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

#26,266
“STI” frequency rank
#4,050
“sum” frequency rank
30316
confusion score

Side-by-Side Comparison

Feature STI sum
Definition Initialism of sexually transmitted infection (also S.T.I.). A quantity obtained by addition or aggregation.

Letter map: STI vs sum

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

3 ch
STI
3 ch
sum

Spelling & dictionary notes on STI vs sum

STI and sum 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 share most of their letters but differ in 2 positions. Our composite confusion score for this pair is 30316, derived from the frequency rank of both members and their visual similarity.

STI is recorded at frequency rank #26,266, classified as anoun. sum is at rank #4,050, tagged as anoun, pronounced /sʌm/.

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 30316, this pair ranks #355,585 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of STI vs sum

Shared letters: s. Private to "STI": it. Private to "sum": mu.

"STI" · 3 letters · shape CCV  ·  "sum" · 3 letters · shape CVC

Frequently Asked Questions

Do "STI" and "sum" mean the same thing in a sentence?
No. They share most of their letters but differ in 2 positions, but the dictionary glosses above give them different meanings, so swapping one for the other changes what the sentence says.
In ordinary English text, does "STI" or "sum" show up more?
"sum" is the more common of the two: it sits at frequency rank #4,050 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.

Useful next steps

Pair "STI" vs "sum" is on the table, pick a follow-up below.

  • Full dictionary entry for "STI" with definition, IPA, and generated misspellings. Word entry
  • Full dictionary entry for "sum" - compare definitions side by side with the headword page. Word entry
  • This pair ranks #355,585 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
  • "STI" and "sum" also get mixed up with nearby pairs, the highest-scored neighbour is "Sif vs STI". Nearby pair

Confusion rank #355,585 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list