What’s the longest word in the English language?

It is:

neumonoultramicroscopicsilicovolcanoconiosis = A lung disease caused by inhalation of silica dust.

Other long words around the world include:

Floccinaucinihilipilification = Act or habit of estimating as worthless. Longest word in Hansard, as used by by Jacob Rees-Mogg

Taumatawhakatangihangakoauauotamateaturipukakapikimaunga-
horonukupokaiwhenuakitanatahu
 Longest-named place in the world, given to a New Zealand hill by the Maoris

Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz = the law concerning the delegation of duties for the supervision of cattle marking and the labelling of beef. Until recently. the longest world in the German language

And finally:

Hippopotomonstrosesquipedaliophobia = the fear of long words

All this information comes from this article.