When a buyer purchases a good each individual item of a certain type is less satisfying that earlier what is this know as?

This phenomenon is known as "diminishing marginal utility." It refers to the decrease in added satisfaction or utility a consumer derives from each additional unit of a good or service consumed. As a buyer purchases more of a good, the pleasure or benefit gained from each subsequent item tends to decline, leading to a reduced incentive to buy additional units at the same price.