An "arco" is a term used in music to describe a specific way of playing string instruments, such as the violin or cello. It involves using a bow to produce sound by drawing it across the strings. This technique allows for a smooth and continuous tone, making it essential for many classical compositions. In architecture, "arco" refers to an arch, which is a curved structure that spans an opening and supports weight above it. Arches are commonly found in buildings, bridges, and aqueducts, showcasing both aesthetic beauty and structural strength. They have been used since ancient times in various cultures.