decrement (noun) – the act or process of decreasing or the amount lost in this process
BREAKDOWN: DE- (away) + CRE- (grow) + -MENT (state of)
— decremental means decreasing or waning in small or gradual steps
This word is built on the root CRE-, which means to grow or increase.
Common CRE- words include crescent, crew, decrease, or increase.
More esoteric CRE- words include accretive and decremental.