Tyrion Lannister, shorter than others due to his dwarfism
Dwarfism is a congenital medical condition that humans can be born with, considered a deformity, which results in those afflicted with it possessing significantly shorter than average height. A person born with this condition is known as a dwarf, and a plural number of such persons are known as dwarfs. The condition of dwarfism is known to have occurred in human populations both in Westeros and in Essos.