A monkey is a hairy primates that usually moves by clinging and leaping on branches. Some species (like vervet monkeys) have prehensile tails that they can use to grip and hold objects. Monkeys and apes are both part of the biological order of primates, but they are separated into two groups: the New World monkeys (in the infraorder Similformes) and the Old World apes and monkeys (in the infraorder Hylobatiformes).
Many types of monkey live in tropical rainforests in Asia, Africa, Central and South America, and elsewhere; others are mountain dwellers (like geladas and golden monkeys) or savanna dwellers (like baboons and giraffes). Some, such as Japanese macaques, are diurnal, meaning they spend most of their time in trees and only occasionally come down to the ground. They often sleep in trees, either alone or snuggled together to stay warm.
Most monkeys are highly social animals, living in troops that include several females with their young and a single male or multiple males. Females may stay with the troop in which they were born, or they might join new troops on reaching adulthood. Males sometimes form their own bands, or harems.
Monkeys communicate with scent and vocalizations, including a series of grunts that echo throughout the forest canopy. They can also use their hands to grasp a branch or object as they move. Like humans, monkeys can learn to do a variety of tasks by watching other monkeys. However, their language skills are limited compared to ours. A 2019 study in the journal Frontiers in Psychology found that Old World monkeys can combine two items into a short sequence of words, but they cannot string together an infinite number of combinations like we can — thus their language is more limited than ours.