fail vs FIS, What's the Difference?

Which to use

“fail” is a verb and “FIS” is a noun - they look or sound alike but fill different roles in a sentence.

#2,441
“fail” frequency rank: #40,245
“FIS” frequency rank: 42686
confusion score

Side-by-Side Comparison

Feature	fail	FIS
Definition	To be unsuccessful.	Initialism of flight information service.

Letter map: fail vs FIS

Shared letters muted; letters that set fail and FIS apart highlighted. Shared run: 2. fail runs 4 letters (CVVC) against FIS's 3 (CVC) - the length gap alone is often enough to separate them once you know to check it.

4 ch

fail

3 ch

FIS

Role in the sentence - fail and FIS

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: fail is averb and FISanoun. On the page they differ by 1 letter(s) in length. Our composite confusion score for this pair is 42686, derived from the frequency rank of both members and their visual similarity.

fail is recorded at frequency rank #2,441, classified as averb, pronounced /feɪl/. FIS is at rank #40,245, 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 42686, this pair ranks #246,998 of 530,003 scored English confusable pairs - roughly mid-pack for confusability.

Orthographic DNA of fail vs FIS

Shared letters: fi. Private to "fail": al. Private to "FIS": s.

"fail" · 4 letters · shape CVVC · "FIS" · 3 letters · shape CVC

Known mistypes of this pair

fail ← afil · faill · fali · ffail · fial

Frequently Asked Questions

Do "fail" and "FIS" mean the same thing in a sentence?

No - they are not even the same part of speech. "fail" is a verb and "FIS" a noun, so a sentence built for one is usually ungrammatical with the other.

In ordinary English text, does "fail" or "FIS" show up more?

"fail" is the more common of the two: it sits at frequency rank #2,441 in our English list, against #40,245 for "FIS". That is a wide gap, so in ordinary text the rarer spelling is the one worth double-checking.

Useful next steps

You've compared "fail" and "FIS". Here's where to go from here.

Full dictionary entry for "fail" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "FIS" - compare definitions side by side with the headword page. Word entry
This pair ranks #246,998 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"fail" and "FIS" also get mixed up with nearby pairs, the highest-scored neighbour is "FIS vs foh". Nearby pair
Recorded mistypes exist for at least one side of this pair, useful when a spell-checker or OCR lands on the wrong form. See mistypes

Confusion rank #246,998 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.