To detect means to discover or notice something that isn't obvious or easy to see. When a doctor detects an illness early, she finds signs of it before the patient feels very sick. When you detect a hint of cinnamon in your grandmother's cookies, you've picked up on that subtle flavor even though you can't see it.

Detection usually requires attention and sometimes special tools or training. A smoke detector senses smoke particles in the air that you might not notice until it's too late. A detective detects clues at a crime scene that other people walk right past. Scientists use instruments to detect distant planets or tiny particles invisible to the human eye.

The word often suggests something hidden or hard to find. You might detect nervousness in your friend's voice, detect a small mistake in your math homework, or detect movement in the bushes while hiking. A lie detector attempts to detect when someone isn't telling the truth by measuring the body's reactions.

When you're trying to detect something, you're being observant and alert, using your senses or your mind to catch what others might miss. The ability to detect details, whether you're reading a mystery novel or conducting a science experiment, often makes the difference between understanding what's really happening and missing the whole story.