substantiation

The act of substantiating or proving; evidence; proof.

noun

1. That which confirms: attestation, authentication, confirmation, corroboration, demonstration, evidence, proof, testament, testimonial, testimony, validation, verification, warrant. See true/false.
2. A physical entity typifying an abstraction: embodiment, exteriorization, externalization, incarnation, manifestation, materialization, objectification, personalization, personification, type. Rhetoric prosopopeia. See substitute.

The noun has 2 meanings:

Meaning #1: additional proof that something that was believed (some fact or hypothesis or theory) is correct
  Synonyms: confirmation, verification, check

Meaning #2: the act of validating; finding or testing the truth of something
  Synonyms: validation, proof