Pneumonoultramicroscopicsilicovolcanoconiosis (/njumnoltrmakrskpkslkovlkenokonioss/ ( listen)) is a word invented by the president of the National Puzzlers' League as a synonym for the disease known as silicosis. It is the longest word in the English language published in a dictionary, the Oxford English Dictionary, which defines it as ''an artificial long word said to mean a lung disease caused by inhaling very fine ash and sand dust.''

Is it true that the longest word in the english language is pneumonoultramicroscopicsilicovolcanoconiosis?
yes