How many letters are in the English dictionary?

In the English lexicon, none is recognized - the longest has 28: antidisestablishmentarianism actually the longest word is floccinaucinihilipilification 29 letters. It means acting worthless.

There are 26 letters in the alphebet. If you want to add the capital letters and lower case letters, it would be 52 letters.

Pneumonoultramicroscopicsilicovolcanoconiosis = 45 letters

There is 1,909 letters in the longest word (english language)

The Second Edition of the Oxford English Dictionary contains full entries for 171,476 words in current use, and 47,156 obsolete words.