The radii of a circle are the line segments that connect the center of the circle to any point on the circle itself. They are all of equal length in a perfect circle, defining its size and shape uniformly from the center outward.
Each individual radius of a circle is called a radius. It is singular and refers to one of these line segments that extend from the center to any point on the circle’s circumference.
“Radii” and “radius” are grammatical forms used to distinguish between singular and plural in English grammar. “Radius” is singular, referring to one line segment from the center to the circumference, while “radii” is the plural form, used when referring to more than one such line segment.
The phrase “1 radii” is grammatically incorrect. The correct singular form is “1 radius.” This represents a single line segment extending from the center of the circle to its circumference, determining its size and spatial dimensions in geometry.