Handedness is an attribute of human beings defined by their unequal distribution of fine motor skill between the left and right. An individual who is more dextrous with the right hand is called right-handed, and one who is more skilled with the left is said to be left-handed. A minority of people are equally skilled with both hands, and are termed ambidextrous. People who demonstrate awkwardness with both hands are said to be ambilevous or ambisinister. There are four main types of handedness:

Right-handedness is the most common. Right-handed people are more dextrous with their right hands when performing a task.

Left-handedness is less common than right-handedness. Left-handed people are more dextrous with their left hands when performing a task. About 17% of people are lefthanded.

Mixed-handedness, also known as cross-dominance, is being able to do different tasks better with different hands. For example, mixed-handed persons might write better with their right hand but throw a ball more efficiently with their left hand. This could also refer to pianists, because different sections of pieces are usually composed to fit the abilities of the different hands, considering that the right hand is usually for melodies and the left-hand, harmonies. However, some people often refer to handedness as the hand that a person uses to write, so this form of handedness is not usually referred to.

Ambidexterity is extremely rare. A true ambidextrous person is able to do any task equally well with either hand. The condition is very rare, although it can be learned (those who master it still tend to sway towards their originally dominant hand.

Most humans that are right-handed prefer to draw their circles and stir beverages counter-clockwise. Laterality in animals is also called limb dominance. Most race tracks are run counter-clockwise, which favors right-side dominant horses, as they take a longer stride with the right foreleg, which helps them turn to the left. Trainers of left eye dominant horses may put a blinder on the left eye to encourage the horse to turn the head slightly to the left and to take a longer step with the right foreleg just as right-side dominant horses do. Parrots tend to favor one foot when grasping objects (for example fruit when feeding). Some studies indicate that most parrots are left footed. Polar bears generally kill their prey using their left paw.