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cornerstone

1 ENTRIES FOUND:
cornerstone /ˈkoɚnɚˌstoʊn/ noun
plural cornerstones
cornerstone
/ˈkoɚnɚˌstoʊn/
noun
plural cornerstones
Britannica Dictionary definition of CORNERSTONE
[count]
: 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