cornerstone

[ kawr-ner-stohn ]
/ ˈkɔr nərˌstoʊn /

noun

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.

Origin of cornerstone

Middle English word dating back to 1250–1300; see origin at corner, stone

Example sentences from the Web for cornerstone

British Dictionary definitions for cornerstone

cornerstone
/ (ˈkɔːnəˌstəʊn) /

noun

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 the cornerstone of the whole argument