What is a radii in mathematics

The radii is the distance from the center of a circle to the edge of the circle

Answer: radii is the plural form of radius. A radius is a straight line from the center of a circle to the circumference of a circle. If you have two or more of them, they are referred to as radii. All radii in a circle will be the same length. The circumference is the outside perimeter of the circle. Its the distamce around a circle.