I'm using Vim 8.0 along with it's excellent spelling feature to check text documents for errors. I need create a custom spelling dictionary by copying the en_us dictionary and modifying it. The modification will swap out all ascii ' [contraction] symbols from the keyboard and use a proper unicode contraction symbol [U+20BC] which is what is used in my project.
For reference, the "typewriter apostrophe" is unicode U+0027 and is an ascii character as well. This is the symbol that Vim Spell determines to be an apostrophe for contractions, and for most users this is probably what's desired. However, there are similar symbols in unicode outside of ascii: U+0219 is a right-single-tic-quotation-mark used in typography (but not on the keyboard or in ascii) It is frequently used with quotations in the print world of publishing, and many times as for contraction words as well. However, the character I need to use is a modifier-letter-apostrophe specifically intended for contractions but not quotations, and this is unicode symbol U+02BC. I will swap U+0027 symbols for U+02BC symbols in my new customized spelling dictionary. I think I will call it something like us_me and use that instead of us_en.
EDIT Vim uses binary dictionaries derived from the Myspell project and are located in /usr/share/vim/vim80/spell/