I. ˈməltəplə̇t noun
( -s )
Etymology: International Scientific Vocabulary multiple (I) + -et
: a spectrum line having several components
II. noun
1. : any of two or more atomic, molecular, or nuclear quantum states that are usually close together in energy and that arise from different relative orientations of angular momenta
2. : a group of spectral frequencies arising from transitions to or from a multiplet quantum state
3. : a group of elementary particles different in charge but similar in other properties (as mass)