flu vs fou, What's the Difference?

Which to use

“flu” is a noun and “fou” is an adjective - they look or sound alike but fill different roles in a sentence.

#7,564
“flu” frequency rank: #48,244
“fou” frequency rank: 55808
confusion score

Side-by-Side Comparison

Feature	flu	fou
Definition	Influenza.	Drunk.

Letter map: flu vs fou

Shared letters muted; letters that set flu and fou apart highlighted. Shared run: 2.

3 ch

flu

3 ch

fou

Role in the sentence - flu and fou

Our dataset has no pronunciation recorded for both members, so the reliable separator here is grammatical: flu is anoun and fouanadjective. On the page they differ by a single letter - l in “flu” becomes o in “fou”. Our composite confusion score for this pair is 55808, derived from the frequency rank of both members and their visual similarity.

flu is recorded at frequency rank #7,564, classified as anoun, pronounced /fluː/. fou is at rank #48,244, tagged as anadj.

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 55808, this pair ranks #130,794 of 530,003 scored English confusable pairs - among the most confusable pairs.

Orthographic DNA of flu vs fou

Shared letters: fu. Private to "flu": l. Private to "fou": o.

"flu" · 3 letters · shape CCV · "fou" · 3 letters · shape CVV

Frequently Asked Questions

Do "flu" and "fou" mean the same thing in a sentence?

No - they are not even the same part of speech. "flu" is a noun and "fou" an adjective, so a sentence built for one is usually ungrammatical with the other.

In ordinary English text, does "flu" or "fou" show up more?

"flu" is the more common of the two: it sits at frequency rank #7,564 in our English list, against #48,244 for "fou". The two are close in frequency, so neither is a safe default; check the meaning rather than guessing.

After this comparison

Done with this confusable. These links stay specific to "flu" and "fou".

Full dictionary entry for "flu" with definition, IPA, and generated misspellings. Word entry
Full dictionary entry for "fou" - compare definitions side by side with the headword page. Word entry
This pair ranks #130,794 of 530,003 scored English confusable pairs in this corpus vintage. Corpus statistics
"flu" and "fou" also get mixed up with nearby pairs, the highest-scored neighbour is "FOMO vs fou". Nearby pair

Confusion rank #130,794 of 530,003 scored English pairs, corpus vintage 2026-09-03, not spelling advice.