there are three groupings of simians; new world monkies, old world monkies and ape
s. a monkey is a simian that is not an ape. prosimians (lemurs, etc.) are not monkies either.
example species of monkies: spider monkey, macaques, baboons, marmosets, etc
example species of non-monkies: humans, chimpanzees, gibbon, lemur, gorilla, orangutang. etc.
monkey: thanks popular culture for making people think that chimpanzees (and other apes) are monkies.