they're all different depending on the size of your circle/sphere buddy :]
The plural of radius is radii.
Radii is a brand of sports footwear.
There are infinite radii in a sphere.
2 radii = one diameter
the single form of radii is radius
A hydrogen atom has the smallest radii.
The covalent radii is for atoms.
It is radii which is the plural of radius
These three radii are of different lengths.
The noun radii is already a plural. The singular is radius.
The word radii has 3 syllables. They are: ra di i
Classically, the plural should be radii, (usually pronounced ray-dee-eye) because 'radius' is a Latin word.However, in modern English, radiuses is acceptable.