To determine means to figure something out, decide it, or make it happen through your choices and actions.

When scientists determine the age of a fossil, they use careful measurements and tests to figure out how old it is. When a judge determines the winner of a science fair, she examines all the projects and decides which one deserves first place. When you determine the answer to a challenging math problem, you work through the steps until you discover the solution.

The word carries a sense of purpose and finality. You don't just guess or wonder: you actively work to reach a solid conclusion or make a firm decision. A detective determines who committed a crime by gathering evidence and eliminating possibilities until the truth becomes clear.

You might also hear people say someone is determined, which describes a person who has decided on a goal and won't give up until they reach it. A determined athlete keeps practicing even when progress feels slow.

The word appears often in serious contexts because determining something matters. Whether you're determining the cause of a problem, the best solution, or your own path forward, you're taking responsibility for reaching a real answer.