Although the Oxford English Dictionary defines more than 750,000 English words, there are only about 860 words that have their letters arranged in alphabetical order. These are known as abecedarian words (from the Latin word, acededarius, meaning “alphabetical”).
Excluding the word “a”, the shortest words with letters in alphabetical order, containing only 2 letters, are: an, be, is, it, no.
The word ace contains 3 letters in alphabetical order.
There are many words with their letters in alphabetical order that contain 6 letters: abhors, accent, access, almost, biopsy, billow, chintz, effort.
The longest word with letters in alphabetical order is Aegilops (8 letters). Technically this is a Latin term: Aegilops is a genus of goat grass, the wild ancestor of modern domestic wheat. In medicine, an aegilops is an abscess or ulcer in the outer or inner corner of the eye. However, the longest English words with letters in alphabetical order, containing 7 letters are: beefily, billowy.
Number with letters in alphabetical order: forty
Number with letters in reverse alphabetical order: one
Longest word with letters in reverse alphabetical order: spoon-feed (9 letters)
Shortest word with all vowels in alphabetical order: aerious (7 letters)
Longest word with all vowels in alphabetical order: pancreaticoduodenostomy (23 letters) followed by adventitious, abstemious, facetious
For further reading: A Curious Dictionary of Language Oddities by Chris Cole, Sterling (1999). rinkworks.com/words/oddities.shtml