HEPATICO­CHOLANGIO­CHOLECYST­ENTERO­STOMIES = a surgical creation of a connection between the gall bladder and a hepatic duct and between the intestine and the gall bladder. This is the longest word in Gould's Medical Dictionary. TETRA­METHYL­DIAMINO­BENZHYDRYL­PHOSPHINOUS = a type of acid. This is the longest chemical term in the Oxford English Dictionary (2nd Ed.). It does not have its own entry but appears under a citation for another word. PNEUMONO­ULTRA­MICRO­SCOPIC­SILICO­VOLCANO­CONIOSIS (also spelled PNEUMONO­ULTRA­MICRO­SCOPIC­SILICO­VOLCANO­KONIOSIS) = a lung disease caused by breathing in particles of siliceous volcanic dust.