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tenth

1

In the United States, a bottle of whiskey, vodka, or similar spirits containing one-tenth of a U.S. gallon; half the size of the much more common fifth, containing one-fifth of a gallon, or ⁴⁄₅ of a quart. See reputed quart.

After the fifth was standardized at 750 milliliters, the name tenth continued in use for a bottle with 375 milliliters (3.4 milliliters less than before).

2

In the United States, a unit of length used by machinists, = one ten-thousandth of an inch.

examples

Tolerances in metalwork often must be calculated to less than one ten-thousandth of an inch (“tenths,” in shop-floor parlance).

Edwin Kiester, Jr.
Don't cut the metal toward you…
Smithsonian, March 1993, page 50.