"Richard Crowley" <[email protected]> wrote in message
news:[email protected]..
> "Jon Harris" wrote ...
>> You may be correct, but common usage seems to be to use
>> acronym for either one. In fact, I've never heard of the word
>> initialism (and neither has the MS spell-checker).
>
> I prefer Merriam-Webster as an arbiter of language
> over the MS spell-checker. www.m-w.com Handy.

MW has the following definition for initialism:

Main Entry: ini·tial·ism
Pronunciation: i-'ni-sh&-"li-z&m
Function: noun
: an acronym formed from initial letters

An initialism is an acronym!

Stuart