The central wedge-shaped member of a masonry arch; also used as a decorative element on arches in wood structures
the most important part, from the idea of the central stone in an arch that keeps the other stones in position - without it, the whole arch would fall down
the symmetrically shaped, wedge-like stone located in a head ring course at the crown of the arch; the final stone placed, thereby closing the arch
A keystone of a policy, system, or process is an important part of it, which is the basis for later developments. Keeping inflation low is the keystone of their economic policy
a stone of the crown string course of an arch; the final stone placed, closing the arch; or symmetrically shaped, wedge-like stone in a head-ring course at the crown of the arch, extending beyond the extradosal and intradosal limits of the voussoirs of adjoining string courses
A stone that blocks one end of a formation of four opposing stones in a row Threats to a keystone may occur when it is part of a pair
Distortion of a projected image in which the top of the image looks broader than the bottom caused by the difference in the distance from the top of image to projector lens as compared to the space between the bottom of the image and the lens
the pronounced centre block in the formation of voussoirs which forms a self supporting arch or window/door head
Keystone (kê´ston´) noun 1) The stone at the top or middle of an arch or vault, which, being wider at the top than at the bottom, enters like a wedge and binds the work; sometimes being projecting and ornamented 2) In a system, that which holds the several parts together; the supporting fact or principle
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"
Each Asytryne requires a keystone for operation The keystone contains the self-contained Attistar for a specific Asytryne, and typically one keystone can only operate the Asytryne it was designed for A keystone Attistar contains all of the security coded hyperwave pattern "ports" needed to interface with the many sub-systems of its Asytryne Some "master" keystones may exist which have the ability to "hack" into the ports of any Asytryne, but these are rare, and even in the best cases they will not be able to operate an Asytryne as well as the keystone AI that was designed for that Asytryne
{i} central and topmost stone in an arch; essential part, something upon which everything depends or rests
A wedged-shaped stone in the center of an arch which acts to keep the arch from collapsing
a group of characters in humorous US silent films (=old films made with no sound) . They are police officers who are very stupid and are always making silly mistakes
Species that interacts with a large number of other species in a community Because of the interactions, the removal of this species can cause widespread changes to community structure Compare with immigrant species, indicator species, and native species
A species whose niche (occupation) in its ecosystem is vital to the survival of many other species The disappearance of keystone species thus leads to a series of extinctions in an ecosystem
A plant or animal that plays a more significant role in the habitat than other species; they provide essential services that are unique Without the work of these key species, the habitat will change significantly
A species of animal on which associated animals depend for support (For example, starfish are keystone species off the coast of British Columbia They feed on clams which would otherwise eat all other sea animals in the region If starfish are removed, the clams flourish, and the marine animal population plunges )