A scanner is a device that converts physical documents, photos, or objects into digital images that can be stored on a computer. When you place a page face-down on a scanner and press a button, a bright light moves across the page while sensors capture every detail, creating a digital copy you can save, edit, email, or print.

Libraries use scanners to preserve old, fragile books by creating digital versions that anyone can read without damaging the originals. Doctors scan X-rays and medical records into computer systems. At airport security, scanners examine luggage to see what's inside without opening bags.

Modern smartphones have made scanning incredibly common. When you take a photo of a worksheet to send to a friend, you're essentially scanning it. Many apps can scan documents, turning your phone's camera into a portable scanner.

The word also describes someone who scans, meaning to look over something quickly but carefully. A crossing guard scans the street for cars before letting students cross. Your eyes might scan a page, looking for your name on a list. In this sense, both the person and the machine are doing similar work: systematically examining something to capture or find specific information.