An aperture is an opening or hole that allows something to pass through, especially light. In photography, the aperture in a camera lens controls how much light reaches the film or sensor. Think of it like the pupil of your eye: in bright sunlight, your pupil gets smaller to let in less light, and in a dark room, it opens wider to let in more. A camera's aperture works the same way.

Photographers adjust the aperture to control their pictures. A wide aperture (a bigger opening) lets in lots of light and makes backgrounds blurry, perfect for portraits where you want someone's face sharp but everything behind them soft. A narrow aperture (a smaller opening) keeps both near and distant objects in focus, which landscape photographers use to capture every detail from nearby flowers to distant mountains.

The word appears in other contexts too. Scientists might study the aperture of a telescope, which determines how much starlight it can gather. An architect might design apertures in a building's walls to control sunlight and ventilation. Wherever you see aperture, think of a carefully sized opening that regulates what passes through it, whether that's light, air, or something else.