This noun denotes demonstration or proof—the showing forth of evidence that establishes a claim. Classical Greek used it for logical proofs, public exhibitions, or testing by examination. Paul uses it in 1 Corinthians 2:4: his message came 'not in persuasive words of wisdom but in demonstration of the Spirit and power.' He contrasts rhetorical cleverness (which could be humanly impressive but ultimately empty) with Spirit-empowered demonstration (which carries divine authority and life-changing power). True proof isn't argumentative sophistication but supernatural effectiveness.