Definition
Proof, in its general sense, means resistant or impervious to something, like 'waterproof' or 'soundproof.' Consider a fortress designed to withstand attack. Unlike something that is easily penetrated, something that is 'proof' offers a barrier. This barrier can be physical, chemical, or conceptual. The concept implies a high degree of resilience or immunity. Essentially, it's a guarantee of protection. Proof establishes certainty against an external threat.