Monosomy is a form of aneuploidy with the presence of only one chromosome (instead of the typical two in humans) from a pair. Partial monosomy occurs when only a portion of the chromosome has one copy, while the rest has two copies.
Human conditions due to monosomy:
Turner syndrome - Women with Turner syndrome typically have one X chromosome instead of the usual two sex chromosomes. Turner syndrome is the only full monosomy that is seen in humans—all other cases of full monosomy are lethal and the individual will not survive development.
Cri du chat syndrome -- (French for "cry of the cat" after the distinctive noise by affected persons' malformed larynx) a partial monosomy caused by a deletion of the end of the short p (from the word petit, French for small) arm of chromosome 5