The longest word in English contains 1,89.819 letters. It is the chemical name of titin, which is the largest known protein. This word is disputed one and has not been included in dictionary (methionyl——-sootherleucine).
Pneumoultramicroscopicsilicovolcanoicconiosis is the longest word found in a major dictionary. It is a technical word, in fact has been coined to describe a disease related to vocanoic eruption.
pseudopseudohypoparathyroiddism is another major technical word, which is again a disease.
However, floccinaucinihilipilification is the widely accepted nontechnical word found in major dictionaries.
Honorificabilitudinitatibus is the longest word Shakespeare used in his play Love’s Labour Lost.
Stengths has single vowel and is the longest in this category.
Rhythms is the longest word without any vowel.
Dematoglyphics, miscongugatedly and uncopyrightables are the longest words without repeated letters.
The word which has vowels only is euouae, which is a musical term.
Now let us laugh it off: Smiles can be considered the longest word as it has miles between s’s. But beleagured can be considered even longer because it has a league.