A hand is a prehensile, multi-fingered organ located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "hand" and fingerprints remarkably similar to human fingerprints) are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
Fingers contain some of the densest areas of nerve endings in the body, and are the richest source of tactile feedback. They also have the greatest positioning capability of the body; thus, the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere, so that handednessthe preferred hand choice for single-handed activities such as writing with a pencil, reflects individual brain functioning.
Some evolutionary anatomists use the term hand to refer to the appendage of digits on the forelimb more generally for example, in the context of whether the three digits of the bird hand involved the same homologous loss of two digits as in the dinosaur hand.
The human hand normally has five digits (four fingers plus one thumb). In other languages, the human hand is said to have five fingers, including the thumb as one of the fingers. It has 27 bones, not including the sesamoid bone, the number of which varies between people, 14 of which are the phalanges (proximal, intermediate and distal) of the fingers and thumb. The metacarpal bones connect the fingers and the carpal bones of the wrist. Each human hand has five metacarpals and eight carpal bones.
Among humans, the hands play an important function in body language and sign language. Likewise the 10 digits of two hands, and the 12 phalanges of 4 fingers (touchable by the thumb) have given rise to number systems and calculation techniques.
Areas of the human hand include:
The palm (Volar), which is the central region of the anterior part of the hand, located superficially to the metacarpus. The skin in this area contains dermal papillae to increase friction, such as are also present on the fingers and used for fingerprints.
The opisthenar area (dorsal) is the corresponding area on the posterior part of the hand.
The heel of the hand is the area anteriorly to the bases of the metacarpal bones, located in the proximal part of the palm. It is the area that sustains most pressure when using the palm of the hand for support, such as in handstand.
There are five digits attached to the hand, notably with a nail fixed to the end in place of the normal claw. The four fingers can be folded over the palm which allows the grasping of objects. Each finger, starting with the one closest to the thumb, has a colloquial name to distinguish it from the others:
- index finger, pointer finger, forefinger, or 2nd digit
- middle finger or long finger or 3rd digit
- ring finger or 4th digit
- little finger, pinky finger, small finger, baby finger, or 5th digit
The thumb (connected to the first metacarpal bone and trapezium) is located on one of the sides, parallel to the arm. A reliable way of identifying human hands is from the presence of opposable thumbs.
A gesture is a form of non-verbal communication or non-vocal communication in which visible bodily actions communicate particular messages, either in place of, or in conjunction with, speech. Gestures include movement of the hands, face, or other parts of the body. Gestures differ from physical non-verbal communication that does not communicate specific messages, such as purely expressive displays, proxemics, or displays of joint attention. Gestures allow individuals to communicate a variety of feelings and thoughts, from contempt and hostility to approval and affection, often together with body language in addition to words when they speak.