An oak is a tree or shrub in the genus Quercus (/ ˈkwɜːrkəs /; Latin "oak tree") of the beech family, Fagaceae. There are approximately 500 extant species of oaks.

oak, (genus Quercus), genus of about 450 species of ornamental and timber trees and shrubs in the beech family (Fagaceae), distributed throughout the north temperate zone and at high altitudes in the tropics.

Oak trees are a group of hardwood trees that belong to the genus Quercus and the beech family, Fagaceae. All types of oak trees are categorized into two groups: white oak trees, and red oak trees. To identify the type of oak tree, you need to look at its bark, leaves, acorns and its general shape.

Oak trees are tall and mostly deciduous. Live oaks, which grow in warmer climates, are evergreen; some species of oak grow as evergreens in warm climates. Oak trees usually have rough, ridged bark. They produce distinctive, tassel-like catkins in spring.