contributory

adj

1. Of, pertaining to, or involving a contribution.
2. Tending to contribute to a result.
3. (obsolete)Paying tribute, tributary.

   “My Lord the great Commander of the worlde, Besides fifteene contributory kings, Hath now in armes ten thouſand Ianiſaries, Mounted on luſty Mauritanian Steeds, […]”

noun

1. A person or thing that contributes.

   “The response to firing is remarkable, and though the 280 lb. pressure seems more in the nature of a reserve for emergencies than a continuous working figure, even with the present-day apology for coal it seldom fell below 250 lb., and could always be brought up to blowing-off point with little difficulty. To this liveliness of steaming the thermic syphons are doubtless the chief contributory.”