Unkindness is the quality of being mean, thoughtless, or cruel to others. When someone acts with unkindness, they might say hurtful things, exclude others on purpose, or ignore someone who needs help. It's the opposite of kindness: instead of treating people with care and consideration, unkindness involves treating them badly or without regard for their feelings.

You might witness unkindness when classmates mock someone for getting an answer wrong, or when a friend deliberately leaves someone out of a game to make them feel unwanted. Unkindness can be dramatic, like bullying, but it can also be subtle, like rolling your eyes when someone is talking or pretending not to hear when someone asks for help.

The word can also refer to a group of ravens. In nature, these clever black birds gather in groups called an unkindness of ravens, though no one knows exactly why they got this strange collective noun. Ravens themselves aren't necessarily mean. The term is just an odd quirk of English.