what is the longest word in the human language?

Well, of course there seems to be some controversy about this. Wikipedia has several examples, noting the Guiness Record holder is the 29 letter floccinaucinihilipilification. Which is defined as "the act of estimating (something) as worthless." Another source note that the 1,185-letter chemical term for "Tobacco Mosaic Virus, Dahlemense Stain", is the longest real word.

At school I remember learning that the longest English word was antidisestablishmentarianism, which has something to do with not supporting the disestablishment of the Church of England as the national religion of the UK...but I prefer sMILEs myself.

supercalafragilisticexpialidocious

PNEUMONOULTRAMICROSCOPIC-SILICOVOLCANOCONIOSIS with is a disease.

It's funny how most people automatically assume English when the question says "human language" :-)

In German, it's possible to concatinate bunch of words together to create a new grammatically correct word. So theoretically, there is no limit to how long a word (in the human language) can be.

supercalafragilisticexpialadocious

Llanfairpwllgwyngyllgogerychwyrndrobwllllantysiliogogogoch which is a village in Wales

I found this site that has many funny long words. it claims to have the longest in the English language.
So between the 1,185 characters Chemical term and the 21 characters “disproportionableness” word, you can probably find your answer.