flue
/flu/noun, adjective
flue is spelled F-L-U-E: 4 letters and one syllable. It appears about once in every 2 million words in written English, the 38,416th most frequent word form (wordfreq, 2021 data). People search “flu vs flue” about 720 times a month (Google, United States). As a noun, flue means “A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace)” (English Wiktionary, September 2026). The plural of flue is flues.
How many letters and syllables are in flue?
| Letters | 4: F-L-U-E |
|---|---|
| Syllables | 1 (from its American pronunciation) |
| In writing | about once in every 2 million words; the 38,416th most frequent word form |
| Wrong spellings searched | none measured in search |
| Pairs people search | |
| Sounds like | |
| Rhymes with | |
| Same letters |
Sources: letters and syllables from the English Wiktionary's hyphenation or pronunciation and the CMU Pronouncing Dictionary; written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media); Bing searches in the United States: the average month from September 2025 to August 2026 (Microsoft Advertising keyword data through DataForSEO, read September 30, 2026); rhymes and same-letter words are computed by PlainSpell from its own word list.
How common is flue?
Flue appears about once in every 2 million words in written English, the 38,416th most frequent word form in the list.
Source: written frequency: wordfreq 3.1 (a 2021 snapshot of Wikipedia, subtitles, news, books, web text and social media).
How do you pronounce flue?
- UK /fluː/
- UK [flʉː]
- US /flu/
Flue has one syllable (counted from its American pronunciation in the CMU Pronouncing Dictionary).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Recordings: LL-Q1860_(eng)-Vealhurl-flue.wav, LL-Q1860_(eng)-عُثمان_(Middle_river_exports)-flue.wav, Wikimedia Commons (author and licence on each file's page).
Words people confuse with flue
Word pairs people search, with the monthly searches for “a vs b” (G: Google, B: Bing, United States).
Sounds like: flew, flu (Wiktionary's homophone list; some hold only in some accents).
Also written: flew.
Sources: Google and Bing searches (September 2025 to August 2026, through DataForSEO); English Wiktionary (homophones, alternative spellings).
What rhymes with flue?
The 12 most written words on PlainSpell end in the same sounds as flue from its last stressed vowel (/u/):
Spelled with the same letters in another order: fuel.
Computed by PlainSpell from the pronunciations in the English Wiktionary (dump of September 2, 2026): a rhyme shares every sound from the last stressed vowel to the end; ordered by written frequency (wordfreq 3.1).
Forms of flue
- flues plural
- more flue comparative
- most flue superlative
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
What does flue mean?
The meanings the English Wiktionary records, quoted as written there (source below).
noun
- 1
A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace).
- 2
An enclosed passageway in which to direct a current of air or other gases along.
- 3
obsoleteA woolly or downy substance; down, nap; a piece of this.
- 4
In an organ flue pipe, the opening between the lower lip and the languet.
adjective
- 1
UKAlternative form of flew (“shallow, flat”).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).
Flue in Spanish, French, German and Portuguese
In the sense pipe that carries gaseous combustion products away from their origin:
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract). Translations are Wiktionary's, by sense; a linked word has its own PlainSpell page.
Where does flue come from?
From Middle English flue, flewe (“mouthpiece of a hunting horn”), of uncertain origin. Perhaps a back-formation from Middle English *flews (mistaken as a plural), from Old English flēwsa (“a flow, flowing, flux”). Alternatively, perhaps an alteration of Middle English floute, fleute, flote (“a pipe”), see English flute. Compare also Middle Dutch vloegh (“groove, channel, flute of a fluted column”).
Source: English Wiktionary, dump of September 2, 2026 (CC BY-SA 4.0), through kaikki.org (Wiktextract).