What’s the Longest Word In the English Language?

If you thought supercalifragilisticexpialidocious was a long word, wait until you try to read the chemical name for Titin, the largest protein ever discovered.

Its chemical name is 189,819 letters long and impossible to copy in its entirety. Still, here’s the first few hundred letters …

Methionyl­threonyl­threonyl­glutaminyl­alanyl­prolyl­threonyl­phenylalanyl­threonyl­glutaminyl­prolyl­leucyl­glutaminyl­seryl­valyl­valyl­valyl­leucyl­glutamyl­glycyl­seryl­threonyl­alanyl­threonyl­phenylalanyl­glutamyl­alanyl­histidyl­isoleucyl­seryl­glycyl­phenylalanyl­prolyl­valyl­prolyl­glutamyl­valyl­seryl­tryptophyl­phenylalanyl­arginyl­aspartyl­glycyl­glutaminyl­valyl­isoleucyl­seryl­threonyl­seryl­threonyl­leucyl­prolyl­glycyl­valyl­glutaminyl­isoleucyl­seryl­phenylalanyl­seryl­aspartyl­glycyl­arginyl­alanyl­lysyl­leucyl­threonyl­isoleucyl­prolyl­alanyl­valyl­threonyl­lysyl­alanyl­asparaginyl­seryl­glycyl­arginyl­tyrosyl­seryl­leucyl­lysyl­alanyl­threonyl­asparaginyl­glycyl­seryl­glycyl­glutaminyl­alanyl­threonyl­seryl­threonyl­alanyl­glutamyl­leucyl­leucyl­valyl­lysyl­alanyl­glutamyl­threonyl­alanyl­prolyl­prolyl­asparaginyl­phenylalanyl­valyl­glutaminyl­arginyl­leucyl­glutaminyl­seryl­methionyl­threonyl­valyl­arginyl­glutaminyl­glycyl­seryl­glutaminyl­valyl­arginyl­leucyl­glutaminyl­valyl­arginyl­valyl­threonyl­glycyl­isoleucyl­prolyl­threonyl­prolyl­valyl­valyl­lysyl­phenylalanyl­tyrosyl­arginyl­aspartyl­glycyl­alanyl­glutamyl­isoleucyl­glutaminyl­seryl­seryl­leucyl­aspartyl­phenylalanyl­glutaminyl­isoleucyl­seryl­glutaminyl­glutamyl­glycyl­aspartyl­leucyl­tyrosyl­seryl­leucyl­leucyl­isoleucyl­alanyl­glutamyl­alanyl­tyrosyl­prolyl­glutamyl­aspartyl­seryl­glycyl­threonyl­tyrosyl­seryl­valyl­asparaginyl­alanyl­threonyl­asparaginyl­seryl­valyl­glycyl­arginyl­alanyl­threonyl­seryl­threonyl­alanyl­glutamyl­leucyl­leucyl­valyl­glutaminyl­glycyl­glutamyl­glutamyl­glutamyl­valyl­prolyl­alanyl­lysyl­lysyl­threonyl­lysyl­threonyl­isoleucyl­valyl­seryl­threonyl­alanyl­glutaminyl­isoleucyl­seryl­glutamyl­seryl­arginyl­glutaminyl­threonyl­arginyl­isoleucyl­glutamyl­lysyl­lysyl­isoleucyl­glutamyl­alanyl­histidyl­phenylalanyl­aspartyl­alanyl­arginyl­seryl­isoleucyl­alanyl­threonyl­valyl­glutamyl­methionyl­valyl­isoleucyl­aspartyl­glycyl­alanyl­alanyl­glycyl­glutaminyl­glutaminyl­leucyl­prolyl­histidyl­lysyl­threonyl­prolyl­prolyl­arginyl­isoleucyl­prolyl­prolyl­lysyl­prolyl­lysyl­seryl­arginyl­seryl­prolyl­threonyl­prolyl­prolyl­seryl­isoleucyl­alanyl­alanyl­lysyl­alanyl­glutaminyl­leucyl­alanyl­arginyl­glutaminyl­glutaminyl­seryl­prolyl­seryl­prolyl­isoleucyl­arginyl­histidyl­seryl­prolyl­seryl­prolyl­valyl­arginyl­histidyl­valyl­arginyl­alanyl­prolyl­threonyl­prolyl­seryl­prolyl­valyl­arginyl­s …

But is it really a word? No. It’s a chemical formula. So, what’s the longest word that’s actually in a dictionary? Here are a few.

  • Pneumonoultramicroscopicsilicovolcanoconiosis, a word that refers to a kind of lung disease, was deliberately made to be the longest word in English.
  • Pseudopseudohypoparathyroidism (30 letters) is an inherited medical disorder.
  • Antidisestablishmentarianism (28 letters) is a political position that developed in 19th-century Britain.
  • Flocci­nauci­nihili­pili­fication at 29 letters describes something as worthless.

But you’re not likely to hear those words in a conversation. What’s the longest word you could actually use? Recently, a computer study discovered that the longest word you’re likely to encounter is uncharacteristically, at 20 letters.

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