Cornerstone

Part of speech: noun

Definitions

1. A crucial element that underpins a structure or concept, representing both a physical block at a building's angle and an essential idea for foundational support and stability
2. A stone laid at the corner of a building marking its starting point ; a primary idea that forms the essential basis of a system or belief
3. A significant stone set at a building's corner during its construction ; a key element that acts as the base for any concept or organization

Etymology: The figurative sense of "cornerstone" comes from the Bible. Psalm 118:22 speaks of a stone that the builders rejected becoming the head of the corner, and the New Testament quotes the image several times, applying it to Christ. Over the centuries the phrase moved from the literal foundation stone of a building to any essential principle that everything else rests upon, so a word for masonry became a metaphor for a belief or system's core. The literal sense is much older and plainer. "Cornerstone" is a compound of "corner" and "stone," and it entered English in Middle English as "corner ston," describing the stone set at the angle where two walls meet. Those first stones were often inscribed or ceremonially placed, which is why the building's starting point and its symbolic beginning became so closely linked.

Synonyms: foundation, basis, keystone, bedrock, support