doublet

noun15

1. •
   A pair of two similar or equal things; couple.
2. •
   A man’s close-fitting jacket, with or without sleeves, worn by European men from the 1400s to the 1600s.

   • Lord Hamlet, with his doublet all unbraced […] — 1599
3. •
   (historical) A man’s waistcoat.

   • I must comfort the weaker vessel, as doublet and hose ought to show itself courageous to petticoat […] — 1598
4. •
   In textual criticism, two different narrative accounts of the same actual event.
5. •
   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.

   • The doublet generally used is that invented by Dr. Wollaston, and consists of two plano-convex lenses placed with their convex sides towards the eye […] — 1855
6. •
   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.
7. •
   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.
8. •
   Either of two dice, each of which, when thrown, has the same number of spots on the face lying uppermost.
9. •
   An imitation gem made of two pieces of glass or crystal with a layer of color between them.
10. •
    Dipole antenna.
11. •
    A word ladder puzzle.
12. •
    (US) A word or phrase set a second time by mistake.
13. •
    A word (or rather, a halfword) consisting of two bytes.
14. •
    A very small flowering plant, Dimeresia howellii.
15. •
    (no longer used) A game somewhat like backgammon.