To validate means to confirm that something is true, correct, or acceptable. When a teacher validates your answer on a math problem, she's checking it and confirming you got it right. When a parking garage validates your parking ticket, they're marking it to show you're allowed to park there, often for free or at a discount.

Validation can also mean recognizing someone's feelings or experiences as real and understandable. If your friend is upset about losing a chess match they worked hard to prepare for, you might validate their disappointment by saying, “I understand why you're frustrated. You put in so much effort.” You're not saying the loss was unfair or that they should have won. You're simply acknowledging that their feelings make sense.

The opposite of validation is invalidation, when someone dismisses or denies what you're experiencing. If that same friend responded to your disappointment by saying, “It's just a game, stop being dramatic,” they'd be invalidating your feelings.

Scientists validate experiments by repeating them to confirm the results hold up. Historians validate ancient documents by checking if they're authentic. In each case, validation means checking carefully and confirming something is legitimate, accurate, or real.