Merriam-Webster Collegiate Dictionary - moiety

 noun  (plural -ties)  Etymology: Middle English moite, from Anglo-French meite, moite, from Late Latin medietat-, medietas, from Latin medius middle — more at mid  Date: 15th century  1.  a. one of two equal parts ; half  b. one of two approximately equal parts  2. one of the portions into which something is divided ; component, part an ether molecule with a benzene ~  3. one of two basic complementary tribal subdivisions