想必这位楼主也是看到 众多的 递减规律头大了

搞清楚前提条件会好一点：消费理论中，商品的是边际效用递减；

生产理论中，单个可变要素情况下是要素报酬递减； 两种可变要素的情况下是边际替代递减；……

还有自己看书吧 只要搞清楚前提，一切都会很清晰的

In economics or daily life, due to diminishing return to anything, basically, marginal anything is commonly decreasing.

Marginal productivity of labor, or capital, marginal utility of goods.

There is no generalized relationship among them. A basic example can be if you increase the amount of capital input, MPK decline, but MPL goes up because assuming no changes in labor amount, each labor has more capital, say more resources, to produce the same good. In other words, they become more productive.