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isospin

noun
iso·​spin | \ ˈī-sə-ˌspin \

Definition of isospin

: 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

First Known Use of isospin

1961, in the meaning defined above

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Time Traveler for isospin

The first known use of isospin was in 1961

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More from Merriam-Webster on isospin

Britannica.com: Encyclopedia article about isospin

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