key,钥匙，关键，stone,石头。因拱顶石形如一把钥匙，同时也最为关键。引申词义主旨，要点。

1. Keeping inflation low is the keystone of their economic policy.

将通货膨胀率保持在较低水平是他们经济政策的主旨。

2. Social justice is the keystone of their political program.

社会公平是他们政治纲领的基本原则.

3. Quantitative measurements of one sort or another serve as the keystone of engineering practice.

定量测定一种或多种成分是环境工程中的重要项目.

4. The keystone to any marriage is one word: " WE ".

任何婚姻的基石只有两个字: “ 我们 ”.

5. Advancing suburban assurance is the difficulty and keystone of domestic insurance enterprise.

发展农村保险是我国保险业发展的难点和重点.