Detection is the act of discovering or noticing something that isn't obvious or is hidden. When a detective works on a case, they're engaged in detection: looking for clues, spotting patterns, and uncovering evidence that others might miss.

Detection happens all around us. A smoke detector senses smoke particles in the air and alerts you to a potential fire. A doctor might use blood tests for the early detection of disease, catching problems before symptoms appear. Scientists use special instruments for the detection of distant planets or tiny particles invisible to our eyes.

The word suggests careful attention, skill, or special tools rather than casual noticing. Detection usually involves actively searching for or identifying something that requires effort to find. You might notice your friend seems sad, but detection would be figuring out why by picking up on subtle clues in what they say and do. Computer programs use fraud detection to spot suspicious patterns in credit card purchases. Wildlife biologists use motion-sensor cameras for the detection of rare animals in remote forests.

Good detection often makes the difference between safety and danger, or between solving a problem and missing it entirely. The earlier the detection, the better the outcome tends to be.