To authenticate something means to prove that it's genuine, real, or true. When a museum authenticates a painting, experts examine it carefully to confirm it was actually created by the artist whose name appears on it, not by someone trying to fool people with a fake. When you authenticate your identity by entering a password, you're proving you're really you and not someone pretending to be you.

Authentication matters because fakes and frauds exist everywhere. Art collectors pay experts to authenticate valuable pieces before spending millions of dollars. Scientists authenticate fossils to make sure they're studying real dinosaur bones, not clever forgeries. Banks authenticate signatures on checks. Libraries authenticate rare books and manuscripts.

The process of authentication usually involves examining evidence closely. An expert might study brushstrokes, test paint samples, or research an artwork's history to authenticate it. A website might send a special code to your phone to authenticate that you're the account's real owner, not a hacker trying to break in.

The related word authentic means real or genuine, like an authentic arrowhead made by Native Americans rather than a replica sold at a gift shop. When something has been properly authenticated, you can trust it's authentic.