A kiss is the touching of the lips to some other thing; usually another person. In modern Western culture it is most commonly an expression of affection. Between people of close acquaintance kissing is done as a greeting or a good-bye, kissing each other on the cheek (or near the cheek, in the air, while cheeks are touching). Relatives may kiss younger children to comfort them or show affection, and vice versa. As an expression of romantic affection or sexual desire it involves two people kissing one another on the lips, and may also involve one person kissing another on various parts of their body.
Kissing is a learned behaviour, related to the grooming behaviour seen between other animals. Many non-human primates also exhibit kissing behavior.
Kissing may also be used to signify reverence and subordination, as in kissing the ring of a king or pope. A kiss can also be rude or done for the sake of irritating or proving one's superiority. A rude kiss or a kiss with a smack is referred to as a buss.
When not an expression of affection, a kiss is a largely symbolic gesture in that the purpose of the kiss is to convey a meaning, such as salutations or subordination, rather than to experience the physical sensations associated with kissing. A kiss can be "blown" using actions of the hand and the mouth. This is used to convey affection usually while parting, when the partners are physically distant but can view each other. Blow kisses are also used when a popular person wishes to convey affection to a large crowd or audience.
In romantic and sexual kissing, the physical sensations are often primary. Thus romantic kissing tends to be more intense and prolonged (see French kiss).
The term is also used for expressions of affection that do not involve the lips. The Eskimo kiss is executed by the two individuals gently rubbing the tips of their noses together. This greeting has other forms. In Malaysia, Charles Darwin reported the following: "The woman squatted with their faces upturned; my attendants stood leaning over them, laid the bridge of their noses at right angles over theirs, and commenced rubbing. It lasted somewhat longer than a hearty handshake with us. During this process they uttered a grunt of satisfaction."
The term Kissing Hands is used to formally describe the appointment of the senior state figures to office by British monarchs. Though in the past, the monarch's hand was actually kissed, this is no longer so. When figures such as the British Prime Minister, cabinet members and diplomatics are formally appointed, they are said to have Kissed Hands. Kissing the hand is still practiced as a romantic flourish, especially in Latin countries.
A kiss in a 1899 photograph
Asymmetry in kissing
In order to avoid clashing noses, a couple will often turn their faces
to one side or another when kissing, so that their heads are at an angle from one another. Often, to make this more comfortable, one person, sitting upright, will support another, perhaps across their lap and in their arms, thus combining hugging and kissing. The person supporting the other is most likely taking the more active role in kissing the other. Writing in Nature, psychologist Oner Güntürkün observed couples kissing in public places such as airports and parks, and showed that the direction of turning is more frequently to the right than the left by a 2:1 ratio. Güntürkün ascribed this asymmetry to a neonatal right side preference.
(data from Nature 421, 711 (13 February 2003); doi:10.1038/421711a)