Which to use
“IAS” is a noun and “iff” is a conjunction - they look or sound alike but fill different roles in a sentence.
- #31,214
- “IAS” frequency rank
- #45,443
- “iff” frequency rank
- 76657
- confusion score
Side-by-Side Comparison
| Feature | IAS | iff |
|---|---|---|
| Definition | Initialism of indicated airspeed. | Abbreviation of if and only if. |
Letter map: IAS vs iff
Shared letters muted; letters that set IAS and iff apart highlighted. Shared run: 1. IAS (VVC) and iff (VCC) run the same length but a different consonant-vowel pattern - the shape difference is usually the fastest tell.
Role in the sentence - IAS and iff
Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: IAS is anoun and iffaconjunction. On the page they share most of their letters but differ in 2 positions. Our composite confusion score for this pair is 76657, derived from the frequency rank of both members and their visual similarity.
IAS is recorded at frequency rank #31,214, classified as anoun. iff is at rank #45,443, tagged as aconj, pronounced /ɪf ən(d)ˈəʊn.li ɪf/.
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 76657, this pair ranks #29,485 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of IAS vs iff
Shared letters: i. Private to "IAS": as. Private to "iff": f.
"IAS" · 3 letters · shape VVC · "iff" · 3 letters · shape VCC
Frequently Asked Questions
Is swapping "IAS" for "iff" ever safe?
Which is more common, "IAS" or "iff"?
What to do next
You've compared "IAS" and "iff". Here's where to go from here.
- Full dictionary entry for "IAS" with definition, IPA, and generated misspellings. Word entry
- Full dictionary entry for "iff" - compare definitions side by side with the headword page. Word entry
- This pair ranks #29,485 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
- "IAS" and "iff" also get mixed up with nearby pairs, the highest-scored neighbour is "iff vs ith". Nearby pair
Confusion rank #29,485 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.