Pinhole (noun)

1. A small hole or aperture, especially one made by a pin or needle.
2. A hole in a camera or similar device that restricts the amount of light entering, used to control exposure and depth of field.

Origin:

Early 19th century: probably so named because of its small size, as a pinhole is typically small enough to be made by a pin.

Examples:

1. The pinhole in the cardboard box was used as a simple camera.
2. The pinhole allowed a beam of light to pass through, illuminating the room.
3. A pinhole can be used to project an image onto a surface.
4. The pinhole in the metal sheet was used to regulate the flow of liquid.
5. The pinhole camera is a basic example of the principle of how a camera works.