aneuploidy (n.)

abnormal number of chromosomes, 1934, from adjective aneuploid (1931), Modern Latin, coined 1922 by G. Täckholm from Greek an- "not, without" (see an- (1)) + euploid, from Greek eu "well, good" (see eu-) + -ploid, from -ploos "fold" (from PIE root *pel- (2) "to fold").