caffein

1. Caffein contained in cola and coffee is the major reason that these drinks are diuretic.
   可乐和咖啡里的咖啡因是这些饮料主要原因。
2. Caffein can improve the blood circulation and firm up facial skin.
   同时，改善血液循环，紧致面部轮廓。

noun

1. a bitter alkaloid found in coffee and tea that is responsible for their stimulating effects

   Synonym:    caffeine