cornerstone Meaning, Definition & Usage

1. noun the fundamental assumptions from which something is begun or developed or calculated or explained
   foundation; basis; groundwork; base; fundament.
   
   • the whole argument rested on a basis of conjecture
2. noun a stone in the exterior of a large and important building; usually carved with a date and laid with appropriate ceremonies
   
3. noun a stone at the outer corner of two intersecting masonry walls
   

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