Marginal utility declining as more of a good is consumed means that total utility:

1. Marginal utility is the addition each new unit makes to the total. 2. As a person receives more of a good, the additional utility from each additional unit of the good declines. 3. Each unit still adds something, so the total keeps rising. 4. It simply rises by smaller and smaller amounts. _Source: OpenStax Principles of Microeconomics for AP(R) Courses 2e (CC BY 4.0), Ch 2 'Choice in a World of Scarcity', sections 2.1-2.3_