A tip (also known as gratuity) is a small amount of money received by some service sector professionals from persons they serve, in addition to or instead of a formally required payment. These transactions are governed by social custom. There are no standing rules or obligations concerning whether to tip (tip is both a noun and a verb), who to tip or how much. It varies from being considered rude to offer a tip (the other may find it degrading, as if (s)he is a beggar) to being considered very stingy not to give one. Also it may be worse to give a very small tip than to give nothing.
Some establishments forbid their employees to accept tips. Others pool tips and divide them to include employees who don't have customer contact.
What occupations are subject to tips varies by locale and culture. In the United States, these people are likely to expect to be tipped:
In some countries (such as Sweden), a tip of the lowest denominations might be given as a sign of approval to a waiter who has given exceptionally good service, but never else.
In the United States, gratuity for waitresses and waiters is generally 15%.
A folk etymology for tip states it is an acronym that stands for "to insure promptness". However, the Oxford English Dictionary states that is is derived from the English thieves' slang word tip, meaning "to pass from one to another". The notion of a stock tip or racing tip is from the same slang.