[dba-Tech] Just curious: How does Word implement its "Add to Dictionary" feature?

I'm guessing that it's some sort of text file stored somewhere on my hard
disk, and assuming that I'm correct, could I edit this file directly and
add the numerous differences between American and correct spelling (i.e.
Canadian and English) of words such as "color" vs. "colour", "honor" vs.
"honour", and so on. I chose simple examples but the problem grows rapidly
more complex as one progresses to larger words.

Does anyone have any insights as to how MS does it inside Word and the
other Office apps?

-- 
Arthur