Casual means relaxed, informal, or not requiring serious effort or commitment. When your teacher says you can wear casual clothes to school on Friday, you don't need to dress up: jeans and a t-shirt work fine. A casual conversation with a friend flows naturally without planning every word.

The word suggests something easygoing rather than formal or intense. A casual reader enjoys books for fun rather than studying them carefully. A casual friendship is pleasant and friendly but not as deep as a close friendship where you share everything. When someone describes their interest in soccer as casual, they mean they enjoy watching games occasionally but aren't passionate fans who know every player's statistics.

Casual can also describe something done without much thought or care. A casual remark is an offhand comment you make without thinking deeply about it. Sometimes this matters: a casual comment about someone's haircut might accidentally hurt their feelings, even though you didn't mean anything by it.

The opposite of casual is formal, serious, or intense. A casual bike ride around the neighborhood differs from training for a race. Understanding when situations call for casual versus serious approaches helps you match your behavior to what's actually needed.