caffein

1. Caffein contained in cola and coffee is the major reason that these drinks are diuretic.
   可乐和咖啡里的***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