keystone

[ kee-stohn ]

/ ˈkiˌstoʊn /

the wedge-shaped piece at the summit of an arch, regarded as holding the other pieces in place.

something on which associated things depend: the keystone of one's philosophy.

Also called keystone sack. Baseball Slang. second base(def 1).

Origin of keystone

First recorded in 1630–40; key¹ + stone

2 basis, principle, foundation, linchpin.

Congress is nearing a vote on the Keystone XL pipeline, and lawmakers made their cases for—and against—it Sunday.

Fact-Checking the Sunday Shows: Jan. 4 |PunditFact.com |January 5, 2015 |DAILY BEAST
Therefore, we should—you guessed it—develop the Canadian tar sands and build the Keystone pipeline.

How Canadian Oilmen Pinkwash the Keystone Pipeline |Jay Michaelson |December 28, 2014 |DAILY BEAST
From the looks of it, mistletoe is a keystone species and plays a crucial role in that forest ecosystem.

Mistletoe is the Vampire of Plants |Helen Thompson |December 21, 2014 |DAILY BEAST
But if Clinton waded into the natural gas debate, she entirely avoided the Keystone one.

Hillary Praises Fracking, Stays Silent on Keystone |David Freedlander |December 2, 2014 |DAILY BEAST

They have made Keystone XL the poster child of their climate-change efforts.

Why the Keystone XL Pipeline May Not Be Built |Robert Bryce |November 19, 2014 |DAILY BEAST
Liberty and fraternity were the two springers of the new arch; its keystone was to be equality.

The Life of Napoleon Bonaparte |William Milligan Sloane
This last terrible experience has been the keystone of my regeneration.

Yolanda: Maid of Burgundy |Charles Major
Over the windows the bricks, of special shapes, were arranged as in a flat arch, with a keystone that jutted slightly.

Helen with the High Hand (2nd ed.) |Arnold Bennett
The keystone of the budget in Mr. Gladstone's conception was the position to be assigned in it to the income-tax.

The Life of William Ewart Gladstone, Vol. 1 (of 3) |John Morley
Political education is like the keystone to the arch—the strength of the whole depends upon it.

Pelham, Complete |Edward Bulwer-Lytton

keystone

/ (ˈkiːˌstəʊn) /

Also called: headstone, quoin the central stone at the top of an arch or the top stone of a dome or vault

something that is necessary to connect or support a number of other related things