1. Plural of duplet; a pair of similar or identical things, especially in physics or chemistry.
Usage: technical; often used in spectroscopy and atomic physics to refer to a pair of closely spaced spectral lines
2. In music, a group of two notes played in the time normally occupied by three notes of the same value.
Usage: musical term; less common than triplet

Examples

• The sodium D-lines appear as duplets in the emission spectrum.
• The physicist observed duplets in the spectral analysis of the element.
• In the musical composition, the composer used duplets to create rhythmic variation.
• The duplets in the atomic spectrum were separated by a small wavelength difference.
• Chemical analysis revealed duplets of peaks in the chromatogram.