What, exactly, is a kiss?

A kiss can be given in private or in public, by men to men, men to women, women to women, adults to children or children to each other. They can be unilateral or reciprocated. They can be on the lips, on the cheek or on any other part of the body. They can be blown in the air. A kiss can express deference, obedience, respect, agreement, reverence, adoration, friendliness, affection, tenderness, love, superiority, inferiority, even insult. There is no such thing as a straightforward kiss.

The Times has an excerpt from The Kiss in History, edited by Karen Harvey.