cancel autocorrect of specific words When I am typing in Mail.app I find that there are particular words that I would like to have the software (or possibly OS) learn.  For some reason the "learn" feature 


does not seem to be the same in this version of OSX as of 10.14.x - I am unable to find it in the contextual menu via control-click
has a separate applet called "spelling and grammar" which does not seem to function


Any recommendations on how I can achieve my goal?
You could try manually adding to your LocalDictionary file, which is in ~/Library/Spelling/LocalDictionary
It's a plain text file, so TextEdit is fine to edit it.
I'm not certain the entries must be in alphabetical order, but it's probably wise to keep them that way.