cornerstone
nounUK /ˈkɔːnəstəʊn/
US /ˈkɔːrnərstoʊn/
A cornerstone is the first big stone at the corner of a building that holds the walls together.
The workers laid the cornerstone before building the rest of the house.
SYNONYMS
OTHER MEANINGS
2. The most important part of something that everything else depends on.
Trust is the cornerstone of a good friendship.
3. A stone that marks a corner of a building or a boundary.
They carved the date into the cornerstone of the old church.
4. A basic idea or rule that supports a whole system.
Fairness is a cornerstone of our school rules.