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July 15, 2024

The 12 Longest Words in English Defined and Explained

The 12 Longest Words in English Defined and Explained

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There are many long words in the English language, but which are the longest? Answers will vary depending on who you ask — especially since some long words, like supercalifragilisticexpialidocious, aren’t actual words. 

Of all the long words in English, there are 12 that I find really useful. Each of these words has at least 20 letters, and you can find them in dictionaries, news articles, and academic texts.

These words can seem challenging because of their complex spellings and meanings. However, as a writer and educator, I’ve found that long words are easier to understand if they’re useful, relatable, and interesting. I’ve helped many students learn long words to improve their reading and writing, and I’m here to do the same for you!

In this article, I’ll share definitions, example sentences, and fascinating facts for 12 of the longest words in English. I’ll also provide handy tips so you can learn other long words.

The 12 longest words in the English language and what they mean 

If you search online for the longest words in the English language, you’ll find a few variations. While some articles cover novelty words like supercalifragilisticexpialidocious or outdated words like disestablishmentarianism, I’ll focus on 12 words that appear in most major dictionaries. 

Let’s explore these words in more detail.   

1. Pneumonoultramicroscopicsilicovolcanoconiosis

How long is it? 45 letters

What does it mean? A lung disease that’s caused by inhaling the silica in volcano ashes

How do I use it in a sentence? “While collecting samples from the dormant volcano, the scientists wore respirators to prevent pneumonoultramicroscopicsilicovolcanoconiosis.”

✨ Fascinating fact: Pneumonoultramicroscopicsilicovolcanoconiosis is the longest word to appear in most major dictionaries and has 19 syllables: Pneu-mo-no-ul-tra-mi-cro-sco-pic-sil-i-co-vol-ca-no-con-i-o-sis

But this word won’t help with concise writing because the more common term for this disease is silicosis. The word can, however, help you understand how longer words are made up of smaller roots with individual meanings:

  • Pneumono (lungs)
  • Microscopic (tiny)
  • Silico (silicon)
  • Volcano (mountain with ashes and lava)
  • Osis (medical condition)

Tip: When you learn the definition of a long word, think about other words that use some of the same roots and have related meanings. For example, pneumonia is a lung infection. These connections will help you remember the new word later.

2. Hippopotomonstrosesquippedaliophobia

How long is it? 36 letters

What does it mean? A phobia of long words

How do I use it in a sentence? “Jeremy felt so nervous while memorizing vocabulary for the exam that he began to wonder if he might have hippopotomonstrosesquippedaliophobia.”

✨ Fascinating fact: “Hippopotomonstrosesquippedaliophobia” is the title of a poem by Aimee Nezhukumatathil about a teacher with a long last name. On the first day of class, the teacher discusses students’ misconceptions about the long last name. Check out this Writer’s Digest interview to learn about Nezhukumatathil’s inspiration for the poem.

3. Pseudopseudohypoparathyroidism

How long is it? 30 letters

What does it mean? A rare thyroid condition that affects bone formation, often leading to short stature and shortened fingers or toes

How do I use it in a sentence? “Dr. Nguyen ran tests for pseudopseudohypoparathyroidism after she noticed the patient had two disproportionately short fingers on each hand.”

✨ Fascinating fact: Pseudopseudohypoparathyroidism is the only English word to repeat the prefix pseudo, which means “fake.” The disorder got its name because it resembles the disorder pseudohypoparathyroidism, even though it’s not the same. 

4. Laryngotracheobronchitis

How long is it? 24 letters

What does it mean? A viral infection that causes swelling and inflammation of the vocal cords, windpipe, and bronchial tubes

How do I use it in a sentence? “When the baby’s fever and cough became worse, Cameron took her to the doctor and learned the baby had laryngotracheobronchitis.”

✨ Fascinating fact: The common name for laryngotracheobronchitis is croup, and it usually only affects children aged 6 and younger. One of the main symptoms is a cough that sounds like a seal barking. Croup mainly affects babies and toddlers because their windpipes are smaller.  

Tip: When you’re unsure how to pronounce a long word like laryngotracheobronchitis, try using an online dictionary with an audio feature. For example, Merriam-Webster and Dictionary.com both provide audio pronunciations with each definition.

5. Hydrochlorofluorocarbons

How long is it? 24 letters

What does it mean? Chemical compounds of hydrogen, chlorine, fluorine, and hydrogen that are mainly used for air conditioning and that also harm the ozone layer

How do I use it in a sentence? “My environmentally-conscious neighbors stopped using their air conditioner because they’re concerned about hydrochlorofluorocarbons.”

✨ Fascinating fact: Almost 200 countries have agreed to stop producing or importing hydrochlorofluorocarbons (HCFCs) by 2030. These plans to phase out HCFCs are part of the Montreal Protocol, an international ozone protection treaty.

Tip: If you’re writing about hydrochlorofluorocarbons, you can use the abbreviation HCFCs, but your readers might need to know what the abbreviation means. So, the first sentence that mentions hydrochlorofluorocarbons should spell out the full word with the abbreviation in parentheses. After you define the abbreviation, you can use HCFCs in the rest of the document. 

The same rule applies to other abbreviations that might be unfamiliar to your readers, such as DMV, which stands for Department of Motor Vehicles.

6. Deinstitutionalization

How long is it? 22 letters

What does it mean? The replacement of hospital-centered care with community-based services for people with mental health disorders and other disabilities

How do I use it in a sentence? “The advocates of deinstitutionalization proposed several alternatives to long-term psychiatric care, such as outpatient therapy and job training.” 

✨ Fascinating fact: Deinstitutionalization was one of many social justice movements that gained more attention during the 1960s. In an effort to support deinstitutionalization, US President John F. Kennedy passed the Community Mental Health Act of 1963, which provided funding for community-based mental health services.  

9. Psychoneuroimmunology

How long is it? 21 letters

What does it mean? A branch of medicine that studies the effects of emotions and other psychological factors on the immune system

How do I use it in a sentence? “Raul became fascinated by psychoneuroimmunology after reading that stress could weaken the immune system.” 

✨ Fascinating fact: Psychoneuroimmunology is a relatively new field of study that began in the 1970s, and it explores both positive and negative effects of emotions on the immune system. For example, psychoneuroimmunology researchers have found that positive experiences, such as laughing or listening to music, improve immunity. 

10. Electroencephalograph

How long is it? 21 letters

What does it mean? The medical device that measures and records brain waves during an electroencephalogram (EEG)

How do I use it in a sentence? “The electroencephalograph I wore during the sleep study was less uncomfortable than I expected.”

✨ Fascinating fact: An electroencephalograph usually includes 16-25 electrodes that are attached to the head with a paste or a cap. Neurologists use electroencephalographs to diagnose brain tumors, seizure disorders, and sleep disorders.  

11. Compartmentalization 

How long is it? 20 letters

What does it mean? The act of dividing something into isolated categories or parts

How do I use it in a sentence? “The pantry included several shelves and bins for convenient compartmentalization.”

✨ Fascinating fact: In psychology, compartmentalization is a defense mechanism that involves dividing thoughts and experiences into separate compartments. A common form of compartmentalization occurs when people with stressful jobs keep their work lives and home lives completely separate. For example, a firefighter might avoid thinking about anything work-related when they’re not on shift. 

12. Uncharacteristically

How long is it? 20 letters

What does it mean? In a way that is inconsistent with someone’s usual habits or beliefs

How do I use it in a sentence? “The valedictorian was uncharacteristically late to the graduation ceremony.”

✨ Fascinating fact: Of all the longest words in the English language, this word is uncharacteristically common. Uncharacteristically occurs in casual conversation far more often than other long English words. 


With these definitions, examples, and facts for 12 of the longest words in the English language, you’re one step closer to using them in conversation or writing. Words such as these can improve your understanding of some fascinating topics.

When you encounter other exceptionally long words while reading or studying, use an online dictionary to explore the definitions and pronunciations. Then, consider how they relate to words and concepts you already know.

Remember, too, that Wordtune can help you write more effectively — whether you use the longest English words or not. Our Editor tool can help you elaborate on long words or check grammar and spelling. We also offer helpful articles about improving your vocabulary, conducting research, and more. 


Is Pneumonoultramicroscopicsilicovolcanoconiosis the longest word in the English language?

With 45 letters, pneumonoultramicroscopicsilicovolcanoconiosis is the longest English word that appears in major dictionaries. This lung disease is more commonly known as silicosis.

What word takes 3 hours to say?

The chemical name for the protein titin would take about 3 hours to pronounce because it has 189,819 letters. Many argue that methionylthreonylthreonylglutaminylarginyl...isoleucine isn’t really a word because it doesn’t commonly occur in conversation or writing.

Is supercalifragilisticexpialidocious a real word?

Most dictionaries don’t include supercalifragilisticexpialidocious because it’s not a real word. This playful song lyric from the film Mary Poppins is a made-up word for “when you have nothing else to say.”