doublet

A pair of two similar or equal things; couple.

One of two or more different words in a language derived from the same etymological root but having different phonological forms (e.g., toucher and toquer in French or shade and shadow in English). See also Appendix:Glossary#doublet.

In textual criticism, two different narrative accounts of the same actual event.

An imitation gem made of two pieces of glass or crystal with a layer of color between them.

A word or phrase set a second time by mistake.

A quantum state of a system with a spin of ½, such that there are two allowed values of the spin component, −½ and +½.

A word (or rather, a halfword) consisting of two bytes.

A very small flowering plant, Dimeresia howellii.

A word ladder puzzle.

An arrangement of two lenses for a microscope, designed to correct spherical aberration and chromatic dispersion, thus rendering the image of an object more clear and distinct.