Detrimental means causing harm or damage to something. When something is detrimental, it makes a situation worse or creates negative effects. If staying up too late playing video games is detrimental to your schoolwork, it means the lack of sleep is hurting your ability to focus and learn. When scientists warn that pollution is detrimental to ocean life, they mean it's actively damaging the health of fish, coral reefs, and other marine creatures.

The word often appears in discussions about choices and their consequences. A coach might explain that skipping practice is detrimental to the team's chances of winning. A doctor might say that too much sugar is detrimental to your health. Notice that detrimental suggests real damage, not just a minor inconvenience. Missing one homework assignment might be unfortunate, but a habit of never studying becomes detrimental to your education.

The opposite of detrimental is beneficial, meaning helpful or positive. When you're making decisions, thinking about whether something will be detrimental or beneficial helps you predict the real effects of your choices.