"A gift is the transfer of a good without an explicit specification of a quid pro quo. The good can be a tangible thing or money, but it also can be intangible, as in the form of time, attention, information or knowledge. A present is a gift and so may be the attention that one person ‘gives’ another, or the time that a person donates to an art institute as a volunteer. Usually a gift entails reciprocity: the giver expects something in return for the gift given. Friends expect friendly gestures in return for their friendly gestures; donors expect some form of appreciation or another; and those who give presents at Christmas expect to receive presents in return. The key to understanding the phenomenon of the gift is the nature of the reciprocity involved."