pro-form

[proh-fawrm] /ˈproʊˌfɔrm/
noun, Grammar
1.
a word used to replace or substitute for a word, phrase, or clause belonging to a given grammatical class, as a pronoun used to replace a noun or noun phrase, there used to replace an adverb or adverbial phrase of place, as in I parked the car near the entrance and left it there, or so used to substitute for a clause, as in Have they come? I think so.
Origin
1960-65
British Dictionary definitions for pro-form

pro-form

noun
1.
a word having grammatical function but assuming the meaning of an antecedent word or phrase for which it substitutes: the word ``does'' is a pro-form for ``understands Greek'' in ``I can't understand Greek but he does''