What is the longest word in the world?

The longest word English word in the dictionary is:

Pneumonoultramicroscopicsilicovolcanoconiosis.

Although pneumonoultramicroscopicsilicovolcanoconiosis is in the dictionary, it's not really a real word. It's a made-up name for lung disease but it was created to mock long medical terms.

What's the longest word not in the dictionary?

The longest word not in the dictionary is the scientific full name for the largest known protein found in the human body.

The scientific name for titin has 189,819 letters. It takes around three hours to say the whole name, and it goes something like this...

Methionylthreonylthreonylglutaminylarginyl...

Find out more about very long words.

Read about the science of language.

Last Updated on January 25, 2025 by Emma Vanstone