“confirm”

To formally approve or sanction something, giving it official validity.

“The board gathered solemnly to ratify the merger that would reshape the industry forever.”

Best for: Strong in legal, political, or formal organizational settings.

To strengthen or support a claim with additional evidence or testimony.

“The second witness stepped forward to corroborate the account already given under oath.”

Best for: Best used in journalistic, legal, or investigative contexts.

To declare or make something officially acceptable, true, or worthy.

“Years of fieldwork finally validated the theory she had defended against ridicule.”

Best for: Works well in scientific, emotional, or bureaucratic registers.

To prove something is genuine, true, or what it claims to be.

“She held the manuscript to the light, struggling to authenticate what could be a lost masterpiece.”

Best for: Ideal for art, identity, historical, or security-related writing.

To affirm or guarantee something with personal authority and confidence.

“He avouched the stranger's innocence before the council without a tremor of doubt.”

Best for: Archaic and weighty; suits formal literary or dramatic prose.

To bear witness to or certify the truth of something through direct knowledge.

“The carved stone itself attested to a civilization far older than anyone had dared imagine.”

Best for: Quietly powerful in historical, legal, or reflective literary contexts.