flue

/fluː/

//fluː// noun

By · According to Wiktionary data (CC BY-SA) ·

"flue" is a 4-letter English headword indexed on PlainSpell.

The verdict

“flue” sits in 20 confusable pairs (corpus #38,401) as a noun. The look-alike neighbours are the real trap.

#38,401
frequency rank, English
2,507
“F” headwords
4
tracked misspellings
20
confusable pairs

According to Wiktionary data (CC BY-SA, analyzed September 3, 2026) - A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace).

Corpus desk

Index EN-flue · flue · English

flue · rank #38,401 · 4 variants · 20 confusables

  • FREQ-MID #38,401
  • LEN-MID 4 letters
  • VOW-2 2 vowels
  • CONFUS-HIGH 20 pairs
  • VAR-LOW 4 variants
  • BOOK-MID 2,507
  • PHOTO-FINISH flirtatious

Nearest frequency peer: flirtatious (-1 rank slots)

Read with this headword: Spelling guide for this pattern

Desk codes from Wiktionary headword shape, FrequencyWords rank tier, confusable-pair count, generated misspelling depth, letter-cohort book size, and photo-finish peer. Not a difficulty grade.

Frequency neighbourhood for “flue”

Lower corpus rank = more everyday usage (inverted bar length for readability)

corpus weight

What this shows Bars show where “flue” sits against the nearest ranked English headwords in the FrequencyWords band, not a reprint of letter-browse containment.

Source FrequencyWords open word-frequency list As of September 3, 2026

Visual similarity to commonly confused words

How many letter changes separate each confused pair (Levenshtein distance, normalized).

flue vs fu
50% similar
flue vs fun
50% similar
flue vs fly
50% similar

Source: PlainSpell confusable corpus (Wiktionary, CC BY-SA).

Key facts for flue
PropertyValue
Headwordflue
LanguageEnglish
Part of speechNoun
IPA/fluː/
Letters4
Frequency rank#38,401
Misspellings tracked4
Confusable pairs20
SourceWiktionary (kaikki.org)

Where “flue” sits in English frequency

Word frequency stretches from the small set of words we reach for constantly (left) out to the long tail barely used once in a while (right).fluelands here:

#1#100#1K#10K#100K
← used constantlyrarely used →

Scale is logarithmic (each tick is 10× rarer). Same rarity band neighbours include “flirtatious” (#38,400), “formulae” (#38,402), “flavoring” (#38,399). Source: FrequencyWords open word-frequency list.

Easy to mix with look-alikes

The spelling risk for flue is neighbouring look-alikes ("fu", "fun", …), not just typos; it is anoun pronounced /fluː/. Frequency #38,401 among 2,507 “F” headwords. 4 recorded senses keep meaning in play.

Our generated misspelling index lists 4 likely wrong-spelling variants for flue, with forms such as "fflue", "fleu", and "fllue". Each of these forms differs from the correct spelling by one small edit: a doubled letter, a dropped silent letter, or a substituted vowel. It also participates in 20 confusable-pair relationships, "fu", "fun", "fly", and more, where similar look or sound leads writers to substitute one word for another in context.

Etymologically, the entry records: 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 Mid… The correct English form is flue, spelled F-L-U-E.

Definition

  1. 1
    A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace).
  2. 2
    An enclosed passageway in which to direct a current of air or other gases along.
  3. 3
    A woolly or downy substance; down, nap; a piece of this.
  4. 4
    In an organ flue pipe, the opening between the lower lip and the languet.

Recorded use

Wiktionary examples

These source excerpts show how flue appears in context. They illustrate usage; the definition above remains the entry’s reference meaning.

  1. It has frequently been a subject of inquiry, whether the ancients were acquainted with chimneys, or open fire-places. In the houses discovered at Herculaneum and Pompeii, there are no chimneys; they all appear to have been warmed by furnaces and flues.
  2. Besides the usual run of machines, planers, millers, automatics, centre lathes, cranes, etc., there were several power stations, the rolling mills for strip material and for 60 ft. rails, and all the steel furnaces with their complicated systems of flues. If variety is the spice of life, then there was plenty here.

Etymology

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”).

This word in other languages

humero(Español)conduit(Français)Abzug(Deutsch)

Common misspellings

Also misspelled as:

  • fflue
  • fleu
  • fllue
  • lfue

Misspelling Pattern Breakdown

How far each generated variant is from the correct spelling of flue - measured in single-character edits (insert, delete, or substitute a letter). Larger bars are easier to catch; one-edit slips are the sneakiest.

fflue1fleu2fllue1lfue2
Edit distance from "flue"

Definitions, pronunciation, and etymology for this entry are drawn from Wiktionary via the kaikki.org structured extract (CC BY-SA); frequency ordering uses the FrequencyWords open word-frequency list (2018 English corpus, MIT). See the methodology for how each field is sourced and updated.

Frequently Asked Questions

How do you spell "flue"?
"flue" is spelled F-L-U-E. The IPA pronunciation is /fluː/.
What does "flue" mean?
As a noun, "flue" means: A pipe or duct that carries gaseous combustion products away from the point of combustion (such as a furnace).
What words are commonly confused with "flue"?
"flue" is commonly confused with "fu", "fun", "fly". These words look or sound similar but have different meanings. PlainSpell provides detailed comparisons for each pair.
How do you pronounce "flue"?
The IPA (International Phonetic Alphabet) transcription for "flue" is /fluː/. Click the speaker icon on the pronunciation badge above to hear it spoken aloud where audio is available.
What is the origin of the word "flue"?
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 alterat... See the full etymology section above for more details.
Is PlainSpell free to use?
Yes, PlainSpell is a completely free word reference. You can look up definitions, pronunciations, confusable pairs, homophones, and spelling corrections across 5 languages without any sign-up or subscription.

Similar English words by spelling shape

Same letter count and similar misspelling depth for "flue", not the corpus desk frequency band.

Same letter count

Frequency-ranked English headwords with 4 letters (nearest by frequency rank).

Haus#38,426huck#38,431juba#38,455kama#38,459

What to do next

You've looked up "flue". Here's where to go from here.

  • "flue" maps to 20 confusable pairs in this vintage; the highest-scored is "fu". View pair
  • 4 edit-distance misspelling variants are generated for spell-check research on this headword. See variants
  • Usage frequency rank #38,401 among English headwords in this corpus. Corpus statistics
  • Browse more English words in the "F" letter cohort. F–Z browse
  • PlainSpell rotates a curated Word of the Day from the English corpus, a passive way to discover vocabulary. Word of the Day

PlainSpell is a reference corpus, not spelling advice. Verify unusual forms in context.

Data Source

Wiktionary (via kaikki.org), licensed under CC BY-SA & GFDL. Word ordering uses an open word-frequency list; misspelling variants are generated by edit-distance from the correct headword.

Source: Wiktionary (via kaikki.org) Structured Wiktionary extract

Source: FrequencyWords open word-frequency list