Keemun1121茶（卫生茶)

Black tea is a variety of that is more oxidized than the , , and varieties. All four varieties are made from leaves of . Black tea is generally stronger in flavor and contains more than the less teas. Two principal varieties of the species are used, the small-leaved Chinese variety plant (C. sinensis subsp. sinensis), also used for green and white teas, and the large-leaved Assamese plant (C. sinensis subsp. assamica), which was traditionally only used for black tea, although in recent years some green has been produced. In and influenced languages, black tea is known as "crimson tea" (, hóngchá; kcha; , hongcha), an accurate description of the colour of the liquid. The term black tea refers to the colour of the oxidized leaves. In Chinese, "black tea" is a commonly used classification for , such as ; in the Western world, "red tea" more commonly refers to , a . While green tea usually loses its flavor within a year, black tea retains its flavour for several years. For this reason, it has long been an article of trade, and even served as a form of in , , and into the 19th century. The tea originally imported to Europe was either green or semi-oxidized. Only in the 19th century did black tea surpass green in popularity.[] Although green tea has recently seen a revival due to its purported health benefits, black tea still accounts for over ninety percent of all tea sold in the West. The expression "black tea" is also used to describe a cup of tea without milk ("served black"), similar to served without milk or cream.