multiplicity (n.)

"involving many parts or relations; consisting of more than one complete individual," 1640s, from French multiple (14c.), from Late Latin multiplus "manifold," from Latin multi- "many, much" (see multi-) + -plus "-fold" (see -plus).

The noun is from 1680s in arithmetic, "a number produced by multiplying another by a whole number," from the adjective. Multiple choice in reference to a question in which the subject selects an answer from several options is attested by 1915. Multiple exposure "repeated exposure of the same frame of film" is recorded by 1891. In psychology, multiple personality is attested by 1886. The chronic, progressive disease multiple sclerosis is so called by 1877, because it occurs in patches (see sclerosis).

"state of being twofold," 1731, from bi- "two" + ending from multiplicity. A useful and non-pejorative alternative to duplicity.