(1):
(n.) Any determinate amount or quantity (as of length, time, heat, value) adopted as a standard of measurement for other amounts or quantities of the same kind.
(2):
(n.) A gold coin of the reign of James I., of the value of twenty shillings.
(3):
(n.) The least whole number; one.
(4):
(n.) A single thing or person.
(5):
(n.) A single thing, as a magnitude or number, regarded as an undivided whole.