| basis(noun, law, idea, base, foundation) |
| foundation(noun, law, hold, block, back) |
| groundwork(noun, hold, block, back, informal) |
| keystone(noun, idea, base, element, foundation) |
| fundamental(noun, part, base, basic, basis) |
| base(noun, hold, block, back, element) |
| fundament(noun, over) |
| core |
| foundation stone(noun, expression, idiom, foundation, keystone) |
| essential(noun, element, foundation, keystone, kingpin) |
| quoin(noun, keystone) |
| crux |
| essence |
| ground(noun, base, basis) |
| principle(noun, law, idea, foundation, essence) |
| root(noun, idea, base, essence, basis) |
| sine qua non(noun, expression, idiom, law, foundation) |
| anchor(noun, element, foundation, pillar, mainstay) |
| footing(noun, hold, block, back, base) |
| heart(noun, law, idea, foundation, essence) |