isospin

noun

iso·​spin ˈī-sə-ˌspin 

: a quantum characteristic of a group of closely related subatomic particles (such as a proton and a neutron) handled mathematically like ordinary spin with the possible orientations in a hypothetical space specifying the number of particles of differing electric charge comprising the group

called also isotopic spin

Examples of isospin in a Sentence

Recent Examples on the Web

In theory, the amplitudes should obey certain relations that apply to the Standard Model, like isospin symmetry, but — as the LHCb collaboration has concluded — measurements show our observations to be inconsistent with those expectations. —Ethan Siegel, Forbes, 12 Mar. 2021

Word History

First Known Use

1961, in the meaning defined above