τεκμήριον tekmḗrion

Meaning

a token (as defining a fact), i.e. criterion of certainty

In the King James Version: infallible proof

Derivation: neuter of a presumed derivative of (a goal or fixed limit);

Where it is used

• Acts 1:3 After His suffering, He presented Himself to them with many convincing proofs that He was alive. He appeared to them over a span of forty days and spoke about the kingdom of God.