bedrock
🇺🇸
/ˈbedrɑːk/
🇬🇧
/ˈbedrɒk/
The most important and basic principles or facts that something is built on.
Trust is the bedrock of a strong friendship.
The solid rock layer beneath the surface of the Earth, which the soil and other materials rest on.
The builders had to dig down to the bedrock to lay the foundation for the new building.