Definition of "productive"
adjective
comparative more productive, superlative most productive
(linguistics, of an affix or word construction rule) Consistently applicable to any of an open set of words.
Quotations
Moreover, this relationship is a productive one, in the sense that when new Adjectives are created (e.g. ginormous concocted out of gigantic and enormous), then the corresponding Adverb form (in this case ginormously) can also be used. And in those exceptional cases where Adverbs do not end in -ly, they generally have the same form as the corresponding Adjective, as with hard, fast, etc.
1988, Andrew Radford, Transformational grammar: a first course, Cambridge, UK: Cambridge University Press, page 138