Which to use
“iff” is a conjunction and “iffy” is an adjective - they look or sound alike but fill different roles in a sentence.
- #45,443
- “iff” frequency rank
- #37,981
- “iffy” frequency rank
- 83424
- confusion score
Side-by-Side Comparison
| Feature | iff | iffy |
|---|---|---|
| Definition | Abbreviation of if and only if. | Of dubious authenticity, legitimacy or legality. |
Where the spellings diverge
Shared letters are muted; the letters that actually set iff and iffy apart are highlighted. They share 3 letters in sequence, which is exactly why the eye skips the difference.
Spelling & Dictionary Insight
These two trip readers on the page rather than in the ear: iff is /ɪf ən(d)ˈəʊn.li ɪf/ while iffy is /ˈɪfi/. Spoken aloud the problem disappears. In writing it persists, because they differ by 1 extra letter(s) - “iff” sits inside “iffy”, and the parts of speech differ too (conjunction vs adjective), which is usually the fastest check. Our composite confusion score for this pair is 83424, derived from the frequency rank of both members and their visual similarity.
iff is recorded at frequency rank #45,443, classified as aconj, pronounced /ɪf ən(d)ˈəʊn.li ɪf/. iffy is at rank #37,981, tagged as anadj, pronounced /ˈɪfi/.
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 83424, this pair ranks #13,855 of 530,003 scored English confusable pairs - among the most confusable pairs.
Orthographic DNA of iff vs iffy
Shared letters: fi. Private to "iff": -. Private to "iffy": y.
"iff" · 3 letters · shape VCC · "iffy" · 4 letters · shape VCCV
Known mistypes of this pair
- iffy ← fify · iffyy · ify · ifyf
Frequency comparison
Frequently Asked Questions
Can "iff" and "iffy" be used interchangeably?
Which is more common, "iff" or "iffy"?
Remembering iff vs iffy
The fastest way to pick the right one every time.
- Check the role first: if you need a conjunction, it's “iff”; for an adjective, it's “iffy”.
- See each word in full, definition, IPA, etymology and its other confusables. Full “iff” entry
- Browse more pairs most likely to be confused. Most confusable