Is there any abbreviations dictionary that I can use for free in a commercial application?
There are great sources of English abbreviations like
that I used as a student, but back then I was not using them for commercial purpose.
One thing I like about those dictionaries (and that would be an additional bonus) is that they offer me a way to choose between possible expansions of a short form based on the domain, e.g., LOTR can be expanded Lord Of The Rings in pop culture, and to Legend Of The Rangers in military domain.
