A monkey is any member of either the New World monkeys or Old World monkeys, two of the three
groupings of simian primates, the third group being the apes. There are 264 known extant species of monkey.
Because of their similarity to monkeys, apes such as chimpanzees and gibbons are often called "monkeys" in informal usage,
though they are not monkeys. Conversely, due to its size (up to 1 m) the Mandrill is often thought to be an ape, but it is
actually an Old World monkey. Also, a few monkey species have the word "ape" in their common name.
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