Add a root word to the dictionary so it picks up plurals, etc.?

[Mali]

Is there a way to add a word to Word's dictionary so that it will pick up
conjugations of the word?

For example, if I add a verb: "eat" to Word's dictionary, I would like it to
recognize eat-ing, eat-s, eat-en, etc.

My specific case is in reference to the noun "setpoint". It is a building
automation systems term that Word's dictionary doesn't contain, and as far as
I can tell, Word doesn't have a pre-packaged supplement for engineering terms
like it does for medical.