Benign means harmless or gentle, not causing damage or danger. When a doctor tells you a growth is benign, she means it's not cancerous and won't spread or threaten your health. That's very different from a malignant tumor, which is dangerous and needs urgent treatment.

The word often describes things that seem potentially worrying but turn out to be safe. A benign mistake is one that doesn't hurt anyone. A benign lie might be telling your grandmother you loved her casserole when you actually found it bland, just to avoid hurting her feelings. A thunderstorm passing through your town might seem frightening, but if it causes no damage, you could call it benign.

You'll also hear benign used to describe people or attitudes that are kind and gentle. A teacher with a benign personality is pleasant and unthreatening, someone students feel comfortable approaching. A benign smile is warm and reassuring, not cold or mocking.

The opposite of benign is usually malignant (actively harmful) or hostile (unfriendly and threatening). When something turns out to be benign, there's often a sense of relief, like discovering that the strange noise in the basement was just the furnace turning on, not an intruder.