keystone

n. central and topmost stone in an arch; essential part, something upon which everything depends or rests

Keystone may refer to:Keystone (architecture), the piece at the apex of an arch or vaultKeystone (cask), a wooden or plastic fitting used in ale casks.Keystone (software), A parser and front-end for ISO C++Keystone species, species that have a larger effect on their environment than is purely due to their abundanceA poetic-theological description of The Book of MormonKeystone module, a type of data connector mounted in walls and patch panelsOperation Keystone during World War IIThe Keystone asterism in the constellation HerculesKeystone School, a private K-12 school in San Antonio, TXKeystone correction, corrects for some types of distortion in projectors The Keystone effect caused by attempting to project an image onto a surface at an angle, as with a projector sitting on a table, pointing upward at a screen, or by photography at an angle
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Noun
1. a central cohesive source of support and stability; "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
(synonym) anchor, mainstay, backbone, linchpin, lynchpin
(hypernym) support
2. the central building block at the top of an arch or vault
(synonym) key, headstone
(hypernym) building block
(hyponym) quoin, coign, coigne
(part-holonym) arch

(n.)
The central or topmost stone of an arch. This in some styles is made different in size from the other voussoirs, or projects, or is decorated with carving. See Illust. of Arch.
  

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