English has plenty of long words, but once you pass 20 letters, the vocabulary starts getting unusual very quickly.
Some extremely long English words come from medicine and science, where smaller Greek and Latin word parts can be combined to describe something very precisely. Others are political or academic terms built from a string of prefixes and suffixes. Then there are famous curiosities such as antidisestablishmentarianism and floccinaucinihilipilification, words now encountered at least as often in discussions about long words as in ordinary conversation.
So what is the longest word in English?
A commonly cited answer is pneumonoultramicroscopicsilicovolcanoconiosis, which contains 45 letters and appears in major dictionaries. It was deliberately coined in the 1930s to be extraordinarily long and is usually described as referring to a lung disease associated with inhaling very fine silica dust.
That answer comes with an important qualification, though. English can produce even longer systematic chemical names, particularly for proteins and complex compounds. Whether those should count as normal English “words” is debatable.
This guide focuses mainly on recognisable dictionary words, established technical terms and a few famous coined expressions containing 20 letters or more.
About This Guide
This guide brings together extremely long English words and explains what they mean, how many letters they contain and roughly how to pronounce them.
The pronunciation guides are written as readable approximations rather than strict IPA. Pronunciation can vary slightly by accent, particularly with highly technical vocabulary that most people rarely say aloud.
Letter counts refer to the spelling shown in this article. Spaces and hyphens would normally complicate exact-letter lists, so the main examples here are written as single words.
The aim isn’t simply to collect the longest strings of letters possible. It is to distinguish between words that have established meanings, specialised scientific terminology and famous linguistic curiosities that became notable largely because of their length.
Who Is This Guide For?
This guide is useful for students, teachers, writers, spelling enthusiasts, word-game fans, English learners and anyone curious about the longest words in English.
It can also help if you have encountered one of these enormous words in a spelling challenge and want to know whether it actually means anything.
Some of the examples are words you could plausibly encounter in normal writing. Others belong almost entirely to medicine, chemistry or discussions about unusual English vocabulary.
Key Takeaways
The longest widely cited dictionary word in English is pneumonoultramicroscopicsilicovolcanoconiosis, at 45 letters, although it was deliberately coined to be exceptionally long.
Antidisestablishmentarianism has 28 letters and is probably the best-known long political word, while floccinaucinihilipilification has 29 letters and means the act of regarding something as worthless.
Many genuine 20+ letter words are technical compounds. Terms such as electroencephalographically, polytetrafluoroethylene and dehydroepiandrosterone become long because they combine several meaningful word parts.
There is no completely uncontested “longest English word” because the answer changes depending on whether you count dictionary entries, systematic chemical names, proper names, deliberately coined words and inflected forms.
Extremely Long English Words at a Glance
| Word | Letters | Meaning |
|---|---|---|
| pneumonoultramicroscopicsilicovolcanoconiosis | 45 | A famously long coined term associated with lung disease from fine silica dust |
| supercalifragilisticexpialidocious | 34 | A playful word expressing something extraordinarily wonderful |
| dichlorodiphenyltrichloroethane | 31 | The full chemical name behind the abbreviation DDT |
| pseudopseudohypoparathyroidism | 30 | A rare inherited condition resembling pseudohypoparathyroidism without the same hormone resistance |
| floccinaucinihilipilification | 29 | The act of regarding something as worthless |
| cyclotrimethylenetrinitramine | 29 | A chemical name for the explosive commonly known as RDX |
| antidisestablishmentarianism | 28 | Opposition to disestablishing an established church |
| electroencephalographically | 27 | In a manner relating to recording the brain’s electrical activity |
| antiestablishmentarianism | 25 | Opposition to or rejection of an established power structure |
| disestablishmentarianism | 24 | Support for ending the official status of an established church |
| electrocardiographically | 24 | In a manner relating to recording the heart’s electrical activity |
| polytetrafluoroethylene | 23 | A synthetic fluoropolymer commonly known as PTFE |
| psychopharmacologically | 23 | In a manner relating to how drugs affect mind, mood or behaviour |
| counterrevolutionaries | 22 | People who oppose or seek to reverse a revolution |
| dehydroepiandrosterone | 22 | A steroid hormone commonly abbreviated DHEA |
| incomprehensibilities | 21 | Things that are impossible or extremely difficult to understand |
| immunoelectrophoresis | 21 | A laboratory technique combining electrophoresis with immune reactions |
| uncharacteristically | 20 | In a way that is not typical of someone or something |
| institutionalization | 20 | The process of establishing something as an institution or placing someone in institutional care |
| counterdemonstration | 20 | A demonstration organised in response to another demonstration |
Dictionary word-finder data confirms many of these exact letter counts, including 23-letter, 24-letter, 27-letter, 28-letter, 29-letter, 31-letter, 34-letter and 45-letter examples.
45 Letters: Pneumonoultramicroscopicsilicovolcanoconiosis
Pneumonoultramicroscopicsilicovolcanoconiosis contains 45 letters.
Approximate pronunciation:
noo-muh-noh-ul-truh-my-kroh-SKOP-ik-sil-ih-koh-vol-kay-noh-koh-nee-OH-sis
It is commonly described as a lung disease caused by inhaling extremely fine silica dust.
However, this is not simply an ordinary medical term that happened to become enormous. The word was deliberately created in 1935 by Everett Smith, then president of the National Puzzlers’ League, partly to produce an exceptionally long English word. Dictionary.com describes it as an obscure term and notes its engineered history.
That makes it an interesting answer to “What is the longest word in the dictionary?” but a less satisfying answer if you’re looking for the longest word that arose naturally through everyday use.
34 Letters: Supercalifragilisticexpialidocious
Supercalifragilisticexpialidocious contains 34 letters.
Approximate pronunciation:
soo-per-kal-ih-fraj-ih-lis-tik-ek-spee-al-ih-DOH-shus
The word is strongly associated with Mary Poppins and is generally used playfully to describe something extraordinarily good or wonderful.
It isn’t a technical term with a precise scientific meaning. Its fame comes from popular culture and from the sheer fun of saying it.
Interestingly, versions of the word existed before the 1964 Disney film, although the familiar spelling was popularised through Mary Poppins.
That puts it in a slightly different category from words such as electroencephalographically: established and recognisable, but intentionally whimsical.
31 Letters: Dichlorodiphenyltrichloroethane
Dichlorodiphenyltrichloroethane contains 31 letters.
Approximate pronunciation:
dye-klor-oh-dye-FEN-il-try-klor-oh-ETH-ayn
You almost certainly know this chemical by a much shorter name:
DDT.
The long form demonstrates one reason chemical vocabulary can become enormous. Chemical names often encode information about molecular composition or structure, meaning several meaningful components may be combined into one word.
In everyday writing, the abbreviation is overwhelmingly more practical.
30 Letters: Pseudopseudohypoparathyroidism
Pseudopseudohypoparathyroidism contains 30 letters.
Approximate pronunciation:
soo-doh-soo-doh-hy-poh-par-uh-THY-royd-iz-um
Despite looking like someone typed pseudo twice by mistake, this is an established medical term.
Pseudopseudohypoparathyroidism is an inherited condition related to pseudohypoparathyroidism. The U.S. National Library of Medicine describes it as having similar physical features but without the abnormal hormone response characteristic of pseudohypoparathyroidism.
The structure becomes easier to understand when broken apart:
pseudo + pseudo + hypo + parathyroid + ism
This is typical of long medical terminology. What appears to be one intimidating word is often several smaller pieces joined together.
29 Letters: Floccinaucinihilipilification
Floccinaucinihilipilification contains 29 letters.
Approximate pronunciation:
flok-suh-naw-suh-ny-hil-uh-pil-uh-fi-KAY-shun
It means the act or habit of regarding something as worthless or of little value.
The word traces back to a collection of Latin expressions associated with worthlessness or triviality.
Ironically, floccinaucinihilipilification is now encountered mainly because people find the word itself unusually valuable as a linguistic curiosity.
It is a legitimate word, but you are considerably more likely to encounter it in an article about long words than in an ordinary meeting.
29 Letters: Cyclotrimethylenetrinitramine
Cyclotrimethylenetrinitramine contains 29 letters.
Approximate pronunciation:
sy-kloh-try-METH-ih-leen-try-NY-truh-meen
This is a chemical name associated with RDX, a high explosive.
Like many very long scientific words, its length results from chemical nomenclature rather than someone deliberately trying to invent an impressive vocabulary word.
It is a useful reminder that scientific terminology tends to dominate lists once you move beyond about 25 letters.
28 Letters: Antidisestablishmentarianism
Antidisestablishmentarianism contains 28 letters.
Approximate pronunciation:
an-tee-dis-uh-stab-lish-men-TAIR-ee-uh-niz-um
For generations, this has been the classic answer children give when asked to name a very long English word.
Its actual meaning is much less familiar.
Antidisestablishmentarianism refers historically to opposition to withdrawing official state support or status from an established church, particularly the Church of England in the 19th century.
The word can be unpacked quite logically:
anti- = against
disestablishment = removing established official status
-arian = a person or position associated with something
-ism = a doctrine, belief or movement
That structure is one reason English can create very long words without inventing entirely new roots.
27 Letters: Electroencephalographically
Electroencephalographically contains 27 letters.
Approximate pronunciation:
ih-lek-troh-en-sef-uh-loh-GRAF-ih-kuh-lee
It means in a manner relating to electroencephalography, the recording of electrical activity in the brain.
The shorter word electroencephalograph refers to an instrument used to measure and record that electrical activity.
This is a good example of how English can extend an already long technical word even further by changing its grammatical form.
25 Letters: Antiestablishmentarianism
Antiestablishmentarianism contains 25 letters.
Approximate pronunciation:
an-tee-ih-stab-lish-men-TAIR-ee-uh-niz-um
It refers broadly to an attitude or ideology opposed to an established political, social or institutional power structure.
It looks very similar to antidisestablishmentarianism, but the meanings are not identical.
Antiestablishmentarianism is opposition to the establishment.
Antidisestablishmentarianism historically means opposition to the process of disestablishing something.
That extra dis- reverses the direction of the argument.
24 Letters: Disestablishmentarianism
Disestablishmentarianism contains 24 letters.
Approximate pronunciation:
dis-ih-stab-lish-men-TAIR-ee-uh-niz-um
It refers to support for disestablishment, particularly ending the special official status of an established church.
The related noun disestablishmentarian describes someone who favours that position.
Put alongside antidisestablishmentarianism, the word shows just how much meaning can be altered by adding a three-letter prefix.
24 Letters: Electrocardiographically
Electrocardiographically contains 24 letters.
Approximate pronunciation:
ih-lek-troh-kar-dee-uh-GRAF-ih-kuh-lee
It means by means of, or in relation to, electrocardiography.
An electrocardiograph records the electrical activity of the heart, producing an electrocardiogram, commonly abbreviated ECG or EKG.
Again, the extraordinary length comes from a relatively systematic combination of meaningful elements rather than arbitrary spelling.
23 Letters: Polytetrafluoroethylene
Polytetrafluoroethylene contains 23 letters.
Approximate pronunciation:
pol-ee-tet-ruh-floor-oh-ETH-ih-leen
It is better known by the abbreviation PTFE.
Polytetrafluoroethylene is a synthetic fluoropolymer used for its low-friction and chemically resistant properties. It is associated with many industrial applications and is also famously used in non-stick coatings.
This is another case where the abbreviated form is much more practical than repeatedly saying the entire chemical name.
23 Letters: Psychopharmacologically
Psychopharmacologically contains 23 letters.
Approximate pronunciation:
sy-koh-far-muh-kuh-LOJ-ih-kuh-lee
The word means in a way relating to psychopharmacology.
Psychopharmacology studies how drugs affect psychological processes, mood, cognition and behaviour.
The word looks daunting, but its pieces are fairly recognisable:
psycho + pharmacology + -ically
Understanding the parts makes both the spelling and the meaning easier.
22 Letters: Counterrevolutionaries
Counterrevolutionaries contains 22 letters.
Approximate pronunciation:
kown-ter-rev-uh-LOO-shuh-nair-eez
A counterrevolutionary is someone who opposes a revolution or seeks to reverse the political or social changes created by one. The plural is counterrevolutionaries.
Unlike many of the chemical and medical words on this page, this is a long word you could realistically encounter in history, politics or journalism.
22 Letters: Dehydroepiandrosterone
Dehydroepiandrosterone contains 22 letters.
Approximate pronunciation:
dee-hy-droh-ep-ee-an-DROS-tuh-rohn
It is commonly abbreviated DHEA.
The U.S. National Library of Medicine describes dehydroepiandrosterone as a steroid produced mainly by the adrenal cortex that can be converted into several other hormones.
As with many medical terms, almost nobody needs to say the full name every time. Abbreviations exist for a reason.
21 Letters: Incomprehensibilities
Incomprehensibilities contains 21 letters.
Approximate pronunciation:
in-kom-prih-hen-suh-BIL-ih-teez
It is the plural of incomprehensibility, meaning something that cannot be understood or the quality of being impossible to comprehend.
This is one of the more interesting long words on the list because it does not belong to a highly specialised branch of science.
It is simply an ordinary English word that has accumulated several layers:
in + comprehend + ible + ity + ies
That makes it a useful example of how normal English morphology can produce very long words.
21 Letters: Immunoelectrophoresis
Immunoelectrophoresis contains 21 letters.
Approximate pronunciation:
im-yoo-noh-ih-lek-troh-foh-REE-sis
This is a laboratory term referring to techniques that combine electrophoresis with immune reactions to identify or analyse proteins.
The length comes from joining two already specialised concepts:
immuno- relating to the immune system
electrophoresis relating to the movement and separation of charged particles under an electric field
Long scientific vocabulary often becomes much less intimidating once you recognise these building blocks.
20 Letters: Uncharacteristically
Uncharacteristically contains 20 letters.
Approximate pronunciation:
un-kar-ik-tuh-RIS-tik-lee
It means in a way that is not typical or characteristic.
For example:
He was uncharacteristically quiet during dinner.
This is probably one of the most usable 20-letter words in everyday English.
Its length comes from adding ordinary prefixes and suffixes to the familiar word character:
un + characteristic + ally
20 Letters: Institutionalization
Institutionalization contains 20 letters.
Approximate pronunciation:
in-stih-too-shuh-nuh-lih-ZAY-shun
It can refer to the process by which something becomes established as a formal institution, practice or system.
It can also refer to placing someone in institutional care, depending on context.
Despite its length, institutionalization is reasonably common in sociology, politics, healthcare and organisational writing.
20 Letters: Counterdemonstration
Counterdemonstration contains 20 letters.
Approximate pronunciation:
kown-ter-dem-un-STRAY-shun
A counterdemonstration is a demonstration organised in response or opposition to another demonstration. Collins gives essentially this definition and recognises both closed and hyphenated presentations in different contexts.
This is another long word whose meaning becomes obvious once you separate its parts:
counter + demonstration
Long does not always mean difficult.
Why Are So Many Extremely Long Words Scientific?
Medicine and science need extremely precise vocabulary.
A doctor, chemist or researcher may need a term that identifies not simply a broad category, but a very particular process, molecule, instrument or condition.
Greek and Latin roots are especially useful because they can be combined systematically.
Consider electroencephalographically:
electro- relates to electricity
encephalo- relates to the brain
-graph- relates to recording or writing
-ically turns the expression into an adverb
The finished word looks intimidating, but its components actually make the meaning fairly logical.
The same principle appears throughout medical vocabulary.
Why Do English Words Get So Long?
English is unusually comfortable combining prefixes, roots and suffixes.
Start with:
establish
Then build:
establishment
Then:
disestablishment
Then:
disestablishmentarian
Then:
disestablishmentarianism
Then add anti- and you reach:
antidisestablishmentarianism
Nothing magical happened. Each piece added another layer of meaning.
This is why simply asking for “the longest possible English word” becomes tricky. In some technical contexts, words can theoretically keep expanding as additional meaningful elements are added.
What Is the Longest Word in the English Dictionary?
If the question means the longest word commonly listed in major general dictionaries, the usual answer is:
pneumonoultramicroscopicsilicovolcanoconiosis
It has 45 letters. Dictionary.com describes it as an obscure term and notes that it was deliberately coined as an exceptionally long word.
That qualification matters.
It is a dictionary word, but it wasn’t born naturally because doctors desperately needed 45 letters to describe a disease. Its creator deliberately engineered an enormous term.
Is Antidisestablishmentarianism the Longest English Word?
No.
At 28 letters, antidisestablishmentarianism is certainly long, but several accepted words are longer.
Floccinaucinihilipilification has 29 letters.
Pseudopseudohypoparathyroidism has 30.
Pneumonoultramicroscopicsilicovolcanoconiosis has 45.
Antidisestablishmentarianism remains famous largely because it is relatively pronounceable and has long been taught as an example of an exceptionally long English word. Merriam-Webster notes that it has enjoyed a much bigger career as a long-word curiosity than as a term people regularly need for its actual political meaning.
What About the Full Chemical Name of Titin?
Discussions about the longest English word often mention the systematic chemical name of titin, an enormous protein.
Written out by naming its amino-acid sequence, the name would contain an extraordinary number of letters and could take hours to pronounce.
However, this is generally not treated as an ordinary dictionary word.
It behaves more like a chemical description generated systematically from the protein’s composition. Dictionary.com similarly notes that the full titin name does not appear as an ordinary entry in major dictionaries or scientific writing.
For that reason, it is usually excluded when people ask about the longest conventional English word.
Does Hippopotomonstrosesquipedaliophobia Really Mean Fear of Long Words?
You may see hippopotomonstrosesquipedaliophobia described online as the fear of long words.
The irony is irresistible, which is probably why the term spreads so easily.
However, it is better treated as a humorous or informal coinage than as a serious clinical diagnosis. The established term sesquipedalian relates to the use of unusually long words, while recognised phobias are not normally diagnosed using hippopotomonstrosesquipedaliophobia as a formal medical label.
This is a useful reminder that appearing on thousands of “funny word” lists does not automatically give a word the same status as established medical terminology.
What Does Sesquipedalian Mean?
A useful word for this entire subject is sesquipedalian.
It can describe unusually long words or a tendency to use them.
The related noun sesquipedalianism refers to the use of long words.
The term goes back to Latin sesquipedalis, literally suggesting something around “a foot and a half long.” Dictionary.com traces the idea back to the Roman poet Horace and his warning about excessively lengthy words.
Fortunately, sesquipedalian itself is comparatively manageable.
Are Longer Words Better Words?
Usually not.
A 29-letter word is not automatically more intelligent, precise or impressive than a six-letter one.
Consider:
His constant floccinaucinihilipilification of my proposal was frustrating.
You could probably write:
He kept dismissing my proposal as worthless.
The second sentence will be much easier for most readers.
Long technical words are useful when their precision matters. Outside specialist contexts, simpler vocabulary is usually clearer.
The interesting thing about extremely long words isn’t that we should use them constantly. It is that they reveal how English builds meaning.
How to Pronounce Very Long Words
Trying to pronounce an enormous word from beginning to end is difficult because the eye tends to treat it as one giant block.
Break it into meaningful pieces instead.
Take:
antidisestablishmentarianism
You can mentally divide it into:
anti + dis + establishment + arian + ism
Likewise:
pseudopseudohypoparathyroidism
becomes:
pseudo + pseudo + hypo + parathyroid + ism
Once you recognise familiar roots and suffixes, the word stops looking quite so impossible.
This technique is also useful for spelling.
How We Count the Letters in Long Words
For the letter counts in this guide, each alphabetical character in the displayed single-word spelling counts as one letter.
For example:
antidisestablishmentarianism = 28 letters
Dictionary word-finder listings independently place it in the 28-letter category.
Hyphens and spaces introduce complications, which is one reason exact-length word lists need clear inclusion rules.
A hyphenated spelling such as counter-revolutionary may be presented differently from the closed form counterrevolutionary. If you’re creating a crossword, spelling puzzle or word-game list, decide whether punctuation is permitted before counting.
Long Words Are Easier When You Understand Their Parts
The most useful lesson from these enormous words is not how to memorise 45 letters.
It is how English builds vocabulary.
Anti- means against.
Counter- suggests opposition or response.
Pseudo- indicates something false, imitative or resembling something else.
Hyper- can indicate excess.
Hypo- often indicates something below, beneath or deficient.
-ism can identify a doctrine, system or condition.
-ology relates to a field of study.
-graph relates to recording or writing.
Once you begin spotting these elements, even intimidating technical words become easier to decode.
Final Thoughts
Extremely long English words are entertaining because they look almost absurd on the page, but they also reveal something genuinely interesting about how language works.
Some, such as uncharacteristically and counterdemonstration, are simply ordinary words that have accumulated several meaningful parts.
Others, including electroencephalographically, dehydroepiandrosterone and pseudopseudohypoparathyroidism, are long because scientific and medical language demands precision.
Then there are the celebrities of the long-word world: antidisestablishmentarianism, floccinaucinihilipilification and pneumonoultramicroscopicsilicovolcanoconiosis. Most people know them not because they need them, but because there is something irresistible about a word that seems determined never to end.
If you’re trying to learn one, don’t memorise it as an uninterrupted chain of letters. Break it apart. In most cases, the smaller pieces tell you exactly why the word is so long in the first place.
Frequently Asked Questions
What is the longest word in English?
Pneumonoultramicroscopicsilicovolcanoconiosis, with 45 letters, is commonly cited as the longest word appearing in major general dictionaries. It was deliberately coined in the 1930s and is associated with a type of lung disease involving fine silica dust.
How many letters are in pneumonoultramicroscopicsilicovolcanoconiosis?
It contains 45 letters.
What does pneumonoultramicroscopicsilicovolcanoconiosis mean?
It is an obscure coined term commonly described as referring to a lung disease caused by inhaling extremely fine silica dust. Its history is unusual because it was deliberately created to be exceptionally long.
What is the longest word most people actually know?
Antidisestablishmentarianism is probably the most famous traditional example. It contains 28 letters and historically refers to opposition to disestablishing an established church.
How many letters are in antidisestablishmentarianism?
Antidisestablishmentarianism has 28 letters.
What does antidisestablishmentarianism mean?
It refers historically to opposition to removing state recognition or support from an established church, particularly the Church of England.
What does floccinaucinihilipilification mean?
Floccinaucinihilipilification means the act of regarding or estimating something as worthless. It contains 29 letters.
What is a 30-letter English word?
Pseudopseudohypoparathyroidism contains 30 letters. It is the name of a rare inherited medical condition related to pseudohypoparathyroidism.
What is a 20-letter English word?
Examples include uncharacteristically, institutionalization and counterdemonstration.
What is a 21-letter word?
Examples include incomprehensibilities and immunoelectrophoresis.
What is a 22-letter word?
Examples include counterrevolutionaries and dehydroepiandrosterone.
What is a 23-letter word?
Examples include polytetrafluoroethylene and psychopharmacologically.
What is a 24-letter word?
Disestablishmentarianism and electrocardiographically both contain 24 letters.
What is a 27-letter word?
Electroencephalographically contains 27 letters.
What is a 29-letter word?
Examples include floccinaucinihilipilification and cyclotrimethylenetrinitramine.
Is supercalifragilisticexpialidocious a real word?
It is an established playful expression strongly associated with Mary Poppins and appears in dictionary word lists. It contains 34 letters, although it does not have the same kind of precise technical meaning as a medical or scientific term.
Is the chemical name of titin the longest word?
It can be vastly longer than ordinary dictionary words when written out systematically, but it is generally excluded from longest-word comparisons because it functions as a generated chemical description rather than a conventional dictionary word.
Why are medical words so long?
Medical terminology frequently combines several Greek and Latin roots, prefixes and suffixes to describe a condition, body part, process or characteristic very precisely. Several meaningful components can therefore become one long word.
What do you call someone who uses very long words?
The adjective sesquipedalian can describe a person or style that uses unusually long words. Sesquipedalianism refers to the tendency or practice of using long words.
Are extremely long words useful in everyday writing?
Usually only when they express a specialised idea that genuinely requires the technical term. In general writing, a shorter and more familiar alternative is normally clearer.
