sour:1. having a sharp, sometimes unpleasant, taste or smell, like a lemon, and not sweet (中文直译过来就是:有一种很明显,有时候不愉悦,尝起来或问题,就像柠檬,以及不甜) acid:1. [ C or U ] any of various usually liquid substances which can react chemically with and sometimes dissolve other materials (中文直译过来就是:任何不同,通常是液体物质,能够进行化学反应,有时候能溶解其他金属) (From:Cambridge Advanced Learner's Dictionary 3rd edition)