- a stone uniting two masonry walls at an intersection.
- a stone representing the nominal starting place in the construction of a monumental building, usually carved with the date and laid with appropriate ceremonies.
- something that is essential, indispensable, or basic: The cornerstone of democratic government is a free press.
- the chief foundation on which something is constructed or developed: The cornerstone of his argument was that all people are created equal.
- a stone at the corner of a wall, uniting two intersecting walls; quoin
- a stone placed at the corner of a building during a ceremony to mark the start of construction
- a person or thing of prime importance; basis
