inradius
Noun
Meaning
(mathematics) the radius of the largest circle that will fit inside any given geometric shape, especially inside a regular polygon
(mathematics) the radius of the largest sphere that will fit inside any given polyhedron
Source: en.wiktionary.orgExamples
Euler's theorem states that the distance d between the circumcenter and the incenter is given by : p.85 : or equivalently : where R is the circumradius and r is the inradius.
The radii of these spheres are called the circumradius, the midradius, and the inradius.