1. a stone that forms the base of a corner of a building
Usage: architectural
2. something of basic importance; a fundamental principle or element

Examples

• The workers carefully placed the cornerstone of the new library.
• The ceremony marked the laying of the cornerstone for the hospital.
• Trust is the cornerstone of any good relationship.
• Education is a cornerstone of democracy.
• Hard work has always been the cornerstone of his success.
• The Constitution serves as the cornerstone of American law.
• Honesty is the cornerstone of good business practices.