noun

• A pair of two similar or equal things; couple.
• (linguistics) 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).
• (literature) In textual criticism, two different narrative accounts of the same actual event.
• (lapidary) An imitation gem made of two pieces of glass or crystal with a layer of color between them.
• (printing, US) A word or phrase set a second time by mistake.
• (quantum mechanics) 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.
• (computing) A word (or rather, a halfword) consisting of two bytes.
• (botany) 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.
• Either of two dice, each of which, when thrown, has the same number of spots on the face lying uppermost.
• (uncountable, obsolete) A game somewhat like backgammon.
• (radio) Dipole antenna.
• (historical) A man’s waistcoat.
• A man’s close-fitting jacket, with or without sleeves, worn by European men from the 1400s to the 1600s.