Noun cornerstone has 3 senses
- basis, base, foundation, fundament, groundwork, cornerstone - the fundamental assumptions from which something is begun or developed or calculated or explained; "the whole argument rested on a basis of conjecture"
--1 is a kind of assumption, supposition, supposal
--1 is a part of explanation
--1 has particulars: meat and potatoes
- cornerstone - a stone in the exterior of a large and important building; usually carved with a date and laid with appropriate ceremonies
--2 is a kind of stone
--2 is a part of building, edifice
- cornerstone - a stone at the outer corner of two intersecting masonry walls
--3 is a kind of stone
--3 is a part of building, edifice
,