Classically, the plural should be radii, (usually pronounced ray-dee-eye) because 'radius' is a Latin word.
However, in modern English, radiuses is acceptable.
It is singular. The plural of "radius" is "radii" with two i's.
The plural of radius is radii. As in "the radii is a straight line extending from the centre of a circle to the circumference"
The singular noun is mass. The plural form is masses.
The plural form of a singular woman is women.
The plural of "she" is "they", so the plural of "she had" is "they had".
The noun radii is already a plural. The singular is radius.
It is singular. The plural of "radius" is "radii" with two i's.
the single form of radii is radius
The plural form of radius is radii.
Radius.
It is singular. The plural is ellipses.
"Is" is the singular form of the verb "to be," used with singular subjects. "Are" is the plural form used with plural subjects.
Vita is singular. The plural form of vita is vitae
This is singular. These is the plural form.
'These' is the plural form of 'this'.
The plural of radius is radii. As in "the radii is a straight line extending from the centre of a circle to the circumference"
The singular form is Dennis. The plural form is Dennises.