keystone

Definition

The top stone of an arch.

Etymology

From key + stone. Definition 4 (retail) possibly originated in the jewelry industry in the magazine called "Jewelers' Circular-Keystone".

Example Sentences

• "The tunnel, which is 1,000 yd. long, had been closed to passenger traffic since November 17, 1949, after some of the keystones had worked loose."
• "Tension between empirical and theoretical knowledge is keystone to sociological and to organizational theories, as early as in Marx's and Weber's frameworks."