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Ri is a traditional Japanese unit of distance, which is sometimes called the "Japanese league", because it is similar to the European league. One ri is equal to 12 960 shaku (one shaku equals to 10/33 m). This is about 3927 meters.

Bohr or bohr radius (a₀) is used in particle physics. One bohr is the mean distance between the proton and the electron in an unexcited hydrogen atom. This unit was named to honor the Danish physicist Niels Bohr (1885-1962), who explained the structure of atoms.