Describe the law of diminishing marginal utility. On what assumptions is this law based?

Please provide the best answer for the statement.

The law of diminishing marginal utility means that as the consumer obtains more units of a given good or service, the consumer receives increasing amounts of total utility or satisfaction. However, the more units of the item that the consumer obtains, the less additional satisfaction or utility each successive unit of the good or service will provide. Total utility increases but by diminishing amounts.
The law assumes that more is preferred to less; that is, more units of a consumer good or service will bring more total utility. But the law also assumes that consumer satisfaction from the first unit obtained is greater than that for successive units. In other words, the intensity of the want or need declines as it is gradually more and more satisfied.