subring
noun
sub·ring ˈsəb-ˌriŋ 
: a subset of a mathematical ring which is itself a ring
Example Sentences
Recent Examples on the Web Photons that make two U-turns around the hole appear as a fainter, thinner subring within the first ring. 
Thomas Lewton, Quanta Magazine, 8 Sep. 2022
Thomas Lewton, Quanta Magazine, 8 Sep. 2022 Word History
First Known Use
1917, in the meaning defined above