noun \-ˌstōn\

: a stone that forms part of a corner in the outside wall of a building and that often shows the date when the building was built

: something of basic importance

Full Definition of CORNERSTONE

:  a stone forming a part of a corner or angle in a wall; specifically :  such a stone laid at a formal ceremony
:  a basic element :  foundation <a cornerstone of foreign policy>


  1. Officials held a ceremony to lay the cornerstone for a new library.
  2. Trust is the cornerstone of their relationship.

First Known Use of CORNERSTONE

13th century

Other Building Terms

batten, cistern, hearth, lath, transom, wainscot


noun    (Concise Encyclopedia)

Ceremonial building block, dated or otherwise inscribed, usually placed in an outer wall of a building to commemorate its dedication. Often the stone is hollowed out to contain newspapers, photographs, or other documents reflecting current customs, with a view to their historical use when the building is remodeled or demolished. Originally placed at a corner, the stone may today be placed elsewhere on the facade.


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