"酸" (suān) 英文是 "sour". 它来源于古英语 "sūr", 源自拉丁语 "sūcus"，意思是酸味。
This lemon is sour. (这个柠檬很酸。)
I don't pke sour cream on my tacos. (我不喜欢在我的墨西哥卷饼上放酸奶油。)
The stock market has been on a sour note lately. (最近股票市场一直不景气。)
酸还可以用来形容人的性格或说话语气，表示不友好或不愉快的。
She had a sour expression on her face. (她脸上有不高兴的表情。)
He had a sour tone in his voice. (他说话语气很不友好。)