What is "multiplet"

n. 1 (context physics English) A spectral line that has multiple components 2 (context chemistry English) A compound peak produced in several forms of spectroscopy 3 (context physics English) Any of several groupings of subatomic particles that share most properties, but have different charges

In physics, multiplet can mean:

• A group of related spectral lines
• A group of related subatomic particles

The best known example is a spin multiplet, which is a group representation of an SU(2) subgroup of the Lorentz algebra. For example, a spin singlet is a trivial representation, a spin doublet is a fundamental representation and a spin triplet is a vector representation.

In other cases, the term multiplet usually refers to the fundamental representation of a gauge algebra. For example, in QCD, quarks are in a multiplet of SU(3).