cornerstone

/ˈkɔːrnərstoʊn/
noun
  1. A stone that forms the base of a corner of a building, often placed during a ceremony to mark the start of construction.
    • The cornerstone of the old church was carved with the year 1723.
    • They placed a time capsule inside the cornerstone of the building.
    • The mayor laid the cornerstone of the new library in a public ceremony.
  2. Something that is essential, fundamental, or the most important part of a system, belief, or organization.
    • The company's cornerstone is its commitment to customer service.
    • Education is the cornerstone of a prosperous society.
    • Trust is the cornerstone of any strong relationship.
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