这是在线词典 Vocabulary.com 为了解释decline的词义而设计的例句，分别举例说明decline作为动词和名词的不同意义。

decline

When something declines, it goes downhill. If you stop working out, your health may decline. If you want it to improve, you should start climbing inclines instead of coasting down declines.

The verb decline means refuse to accept, but the noun decline means a downward slope (the opposite of an incline), or a decrease in quality. At the gym, the treadmill has an incline button to control how steep your climb is. Sadly, there's no button for decline, which would be much easier. Both words contain cline, or "to bend." The prefix tells you which way the bend goes. Decline implies a going, or turning, down.

读完这段解释，你就应该明白黑体部分语法结构和意义。如果你还是不理解，说明你的英语水平不适宜读英英词典释义，忘掉这个句子，找简单一些的读物练习英语阅读理解。