Keystone

Keystone is a term used in architecture to describe the central, wedge-shaped stone in an arch, which holds all the other stones in place. The term is also used metaphorically to refer to the central principle or part of a policy, system, etc., on which all else depends.

Architecture

In architecture, a keystone is the wedge-shaped stone piece at the apex of a masonry arch, or the generally round one at the apex of a vault. In both cases it is the final piece placed during construction and locks all the stones into position, allowing the arch or vault to bear weight. Although a masonry arch or vault cannot be self-supporting until the keystone is placed, the keystone experiences the least stress of any of the voussoirs, due to its position at the apex.

Ecology

In ecology, the term keystone species is used to describe a species that has a disproportionately large effect on its environment relative to its abundance. Such species are described as playing a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community.

See also

• Arch
• Vault (architecture)
• Voussoir
• Keystone species

References

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