The longest word in the major English language dictionaries is
( 45 letters)
Meaning: a disease caused by the prolonged inhalation of fine siliceous dust, specifically from a volcano.
Also spelled pneumonoultramicroscopicsilicovolcanokoniosis
Research has discovered that this word was originally a hoax: medically, it is the same as silicosis.
The Oxford English Dictionary contains
pseudopseudohypoparathyroidism (30 letters)
Meaning: an incomplete form of pseudohypoparathyroidism marked by the same constitutional features but by normal levels of calcium and phosphorus in the blood serum.
The longest non-technical word in major dictionaries is
floccinaucinihilipilification (29 letters)
Meaning: The action or habit of judging something to be worthless.
1741: William Shenstone, William Shenstone, Letters,
”I loved him for nothing so much as his flocci-nauci-nihili-pili-fication of money.”
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