A kiss (from Old English cyssan "to kiss," in turn from coss "a kiss," perhaps onomatopoeic) is the touching with the lips. The scientific name for kissing is .
Origins

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Anthropologists have not reached a consensus as to whether kissing is a learned or an instinctive behavior. It may be related to grooming behavior also seen between other animals, or arising as a result of mothers premasticating food for their children. Kissing allows prospective mates to smell and taste each other's pheromones for biological compatibility. Women are subconsciously more attracted to men whose major histocompatibility complex portion of their genome is different than her own, leading to offspring with resistance to a greater number of diseases, and thus having a better chance of survival.
This explains why couples are more likely to bond if they have the right "chemistry". Many primates also exhibit kissing behavior.

Kissing as affection

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In modern Western culture, kissing is most commonly an expression of affection. This is unlike many parts of the world where kissing is viewed as a means of respecting others.

Between people of close acquaintance, a kiss, often reciprocal, is offered as a greeting or farewell. This kind of kiss is typically made by brief contact of puckered lips to the skin of the cheek or no contact at all, and merely performed in the air near the cheek with the cheeks touching. Such kissing is a common greeting in European and Latin American countries between a man and a woman or between two women but also by two men in part of the Middle East and parts of Europe and Latin America. People sometimes kiss children to comfort them or show affection, and vice versa. This usually takes place on the forehead or cheek.

As an expression of romantic affection or sexual desire, kissing involves two people kissing one another on the lips, usually with much more intensity, and for a considerably longer period of time. In more passionate kissing couples may open their mouths, suck on each other's lips, or move their tongues into each others' mouths (see French kiss). Sexual kissing may also involve one person kissing another on various parts of the body (see Foreplay).

In romantic and sexual kissing, the physical sensations are often of primary importance.
One might find it stimulating if their partner moved their tongue in small circles against their own, or bite the lips gently. Caution should be exercised, as others may find the biting of lips distasteful and displeasing, not enjoying it.

Kissing as symbolism

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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. Kisses on the cheek as salutations are traditional in many parts of continental Europe, and the number of kisses, alternating cheeks, depends on which region one comes from.

Kissing may also be used...