Insincerity means saying or doing things you don't really mean, pretending to feel something you don't actually feel. When someone compliments your drawing but you can tell from their flat voice and quick glance that they don't really like it, that's insincerity. When a student apologizes to a teacher just to avoid trouble, without feeling sorry at all, that's an insincere apology.

An insincere person might smile while saying mean things, or promise to help when they have no intention of following through. You can usually sense insincerity in someone's tone of voice, their body language, or the way their words and actions don't quite match.

Insincerity hurts relationships because trust depends on believing what people say and do. When you discover that someone's friendliness was insincere, it stings more than if they'd been honestly distant from the start. While everyone occasionally says polite things they don't fully mean (like thanking Aunt Martha for the itchy sweater), habitual insincerity makes it impossible for others to know what you truly think or feel. People value sincerity because it lets them know where they really stand with you.