To oppose means to actively disagree with something or work against it. When you oppose an idea, you don't just dislike it: you speak up, take action, or try to stop it from happening. If your class votes on whether to have a field day, and you think it's a bad idea because of scheduling conflicts, you might oppose the plan by explaining your concerns and voting against it.

Opposition shows up everywhere in daily life. In a debate, one team opposes the other's arguments. In sports, opposing teams compete against each other. In government, elected officials often oppose policies they believe will harm their communities. Scientists oppose theories they think are incorrect by presenting evidence and alternative explanations.

Notice that opposing something doesn't mean being mean or unreasonable. You can oppose an idea respectfully by offering thoughtful reasons. When your friend suggests a movie you don't want to see, you might oppose their choice by suggesting a different one everyone would enjoy. Good opposition involves explaining why you disagree and what you think would work better.