backbone

a central cohesive source of support and stability

• “faith is his anchor”
• “the keystone of campaign reform was the ban on soft money”
• “he is the linchpin of this firm”

fortitude and determination

• “he didn”

the series of vertebrae forming the axis of the skeleton and protecting the spinal cord

• “the fall broke his back”

the part of a network that connects other networks together

• “the backbone is the part of a communication network that carries the heaviest traffic”