Meaning of cornerstone

cor•ner•stone

Pronunciation: (kôr'nur-stōn"), [key]
— n.
  1. a stone uniting two masonry walls at an intersection.
  2. a stone representing the nominal starting place in the construction of a monumental building, usually carved with the date and laid with appropriate ceremonies.
  3. something that is essential, indispensable, or basic: The cornerstone of democratic government is a free press.
  4. the chief foundation on which something is constructed or developed: The cornerstone of his argument was that all people are created equal.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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