A semi-circle is a two-dimensional shape that represents half of a circle. It is formed by cutting a full circle along its diameter, resulting in a curved edge and a straight edge. The curved part is called the arc, while the straight edge is the diameter. Semi-circles are often used in various fields, including architecture and design, to create visually appealing structures. In mathematics, the semi-circle is important for understanding properties of circles and angles. The area of a semi-circle can be calculated using the formula A = (πr²)/2, where r is the radius. Semi-circles also appear in real-life applications, such as in the design of bridges and amphitheaters.