If or iff?
if is a conjunction meaning “Supposing that, assuming that, in the circumstances that; suppositive used to…”; iff is a conjunction meaning “Abbreviation of if and only if”. In written English (wordfreq, 2021 data) if is about 6,918 times as common as iff.
What is the difference between if and iff?
| if | iff | |
|---|---|---|
| Part of speech | conjunction, noun | conjunction, noun |
| Meaning | Supposing that, assuming that, in the circumstances that; suppositive used to introduce a condition that may be (or prove to be) either true or false A keyword that invokes conditional processing: in the event that a given condition is true, execute the given statement(s) (otherwise execute other statements) informalAn uncertainty, possibility, condition, doubt etc | |
| Example | I'll do it next week if I have time | A rectangle is a square iff all four of its sides have the same length |
| Forms | eef, ifen, iffen, if'n | none |
| Pronunciation | /ɪf/ /ɪv/ | /ɪf ən(d)ˈəʊn.li ɪf/ /ɪf ən(d)ˈoʊn.li ɪf/ |
| In writing | 2,951 times per million words | about once in every 2 million words |
Sources: if and iff in the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
Every current meaning of if and iff
if
- 1
Supposing that, assuming that, in the circumstances that; suppositive used to introduce a condition that may be (or prove to be) either true or false
I'll do it next week if I have time
- 2
informalAn uncertainty, possibility, condition, doubt etc
The board can't approve this project; there are too many ifs
- 3
Initialism of interactive fiction
- 4
A keyword that invokes conditional processing: in the event that a given condition is true, execute the given statement(s) (otherwise execute other statements)
if A then B else C
- 5
Initialism of impact factor
- 6
Supposing that; used with past or past perfect subjunctive to indicate a counterfactual or hypothetical condition
If she hadn't told me, I wouldn't know
- 7
Initialism of intermediate filament
- 8
Even if; even in the circumstances that
I wouldn't marry you if you were the last man on earth
iff
- 1
Abbreviation of if and only if
A rectangle is a square iff all four of its sides have the same length
- 2
Initialism of identification friend or foe
Source: the English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0); obsolete, archaic, dialect and rare senses left out.
Which is more common, if or iff?
if appears 2,951 times per million words; iff about once in every 2 million words.
if 2,951 times per million wordsiff about once in every 2 million words
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How many people search if vs iff?
“if vs iff” is searched about 90 times a month on Google and 20 on Bing in the United States. Google counts close variants of a query together (“iff vs if”, “if or iff”).
Sources: Google Ads keyword data through DataForSEO and Microsoft Advertising keyword data through DataForSEO, the average month from September 2025 to August 2026.