Chai (Hindi: ???, Urdu: ???) is simply the word for "tea" in much of South Asia and many other parts of the world.. For the etymology of chai and related words see Etymology and cognates of tea. Although coffee is a more popular beverage in some southern parts of India, chai is ubiquitous throughout South Asia, where street vendors called "chai wallahs" (sometimes spelled "chaiwalas") are a common sight. Chai is also a popular item in the genre of South Asian restaurants known as Irani cafÃ©s or Chai Khanas. The traditional chai-brewing process actively boils the tea leaves over sustained heat. Chai prepared in this manner has a caffeine level comparable to coffee, as the prolonged boiling produces a more robust beverage than quiescently steeping the tea leaves in hot (but not boiling) water. For more information about international preparation methods and consumption patterns, see Tea culture. A concentrate is a form of substance which has had the majority of its base component (in the case of a liquid: the solvent) removed. Typically this will be the removal of water from a solution or suspension such as the removal of water from fruit juice. One benefit of producing a concentrate is that of a reduction in weight and volume for transportation as the concentrate can be re-constituted at the time of usage by the addition of the solvent.