A moiety is one of two equal parts. If you cut a sandwich in half, you can have one moiety for lunch and give the other moiety to a pigeon.
One moiety plus one moiety equals a whole. Moiety is a synonym for the noun half; a semicircle or your better half can be referred to as a moiety. In anthropology, moiety is used to describe one of two distinct groups of a tribe. Moiety can also mean "a part" in general, as Shakespeare used it in Antony and Cleopatra: "The death of Antony / Is not a single doom; in the name lay / A moiety of the world."
