The longest word which appears in William Shakespeare’s works is the 27-letter honorific­abilitud­initatibus, appearing in Love’s Labour’s Lost. This is arguably an English word (rather than Latin), only because it was Shakespeare who used it.

The longest word I personally can think of is “Supercalifragilisticexpiali docious”. I had to put a space in this cuz Yahoo doesn’t like long words.

Okay … you asked for it….

Acetylcholinesterase

bronchoesophagoastomy

duodenojejunal

gnathopalatoschisis

Osteochondromatosis

prosthodontics

Pneumonoultramicroscopicsilicovolcanosconiosis

Tetrahydrogestrinone

Uvulopalatopharyngoplasty

Okay and here is the whopper….

Pneumonoultramicroscopicsilicovolcanosconiosis

http://www.medterms.com/script/main/art.asp?articlekey=22547

Pneumonoultramicroscopicsilicovolcanosconiosis: Allegedly, “a lung disease caused by the inhalation of very fine silicate or quartz dust.” The word was invented by compounding pneumo-(lung) + ultramicroscopic + silicon + volcano + coniosis, from the Greek konis (dust). In fact, pneumonoultramicroscopicsilicovolcanosconiosis means nothing. It is a factitious and fictitious word that was created as a spoof of the many long run-on terms found in medicine.

Antidisestablishmentarianism- opposition to the withdrawal of state support or recognition from an established church, esp. the Anglican Church in 19th-century England.

From “Mary Poppins”.

when I was very young I thought elephant was the biggest word in the world! lol