Detriment means harm or damage that makes something worse. When something happens to your detriment, it works against you or hurts your chances of success.

If you stay up too late playing video games on a school night, it will be to the detriment of your performance the next day: you'll be tired, less focused, and won't do your best work. A basketball team that skips practice does so to their own detriment because they won't be as prepared for their next game.

The word often appears when describing how one choice creates problems for something else. Spending all your time on one subject might improve that grade but prove detrimental to your other classes. A factory that pollutes a river causes detriment to the fish and plants living there.

Something detrimental actively causes harm rather than simply failing to help. Forgetting to water a plant once might not help it, but pouring salt on its roots would be detrimental because it would actually damage the plant. When coaches warn that poor sportsmanship is detrimental to team morale, they mean it actively hurts how well the team works together.