The device used for measuring angles is called a protractor. Protractors are typically semi-circular and are marked with degrees from 0 to 180, although full-circle protractors extend this range from 0 to 360 degrees. They are commonly used in geometry, drafting, and various engineering applications. By aligning one side of the angle with the base line of the protractor, users can easily read the degree measurement of the angle across the curved edge. Protractors may also come in digital forms, enhancing precision and ease of use in various technical fields.