A primate (/ˈpraɪmeɪt/ PRY-mayt) is a mammal of the order Primates (Latin: "prime, first rank"). In taxonomy, primates include two distinct lineages, strepsirrhines and haplorhines. Primates arose from ancestors that lived in the trees of tropical forests; many primate characteristics represent adaptations to life in this challenging three-dimensional environment. Most primate species remain at least partly arboreal.