词：sour
英英释义：if a relationship or someone's attitude sours, or if something sours it, it becomes unfriendly or unfavorable
例句：Many friendships sour over borrowed money.
2. 为什么选这个词？
“sour”作动词意思是“恶化”“使......变糟”。
= compound 和 worsen
很多朋友关系是因为借钱而弄僵的，就可以说：
Many friendships sour over borrowed money.
印度和巴基斯坦在领土问题上的争议使得两国关系急转直下，我们就可以说：
The territorial dispute between India and Pakistan soured bilateral relations.
类似的用法也出现在了另一篇《经济学人》文章中：
The once-cordial relationship between Mr Trump and Deutsche has soured.
《经济学人》在一篇写美国经济的文章中也出现了 sour：
Business confidence had soured and the housing market, so often a leading indicator of economic trouble, had sagged.（这句中 confidence 和 sour 这组搭配出现频率要远低于 relationship/relations 和 sour 这组搭配，可以记下来）
3. 怎样学会使用这个词？
1）翻译下面的句子：
他和母亲的关系突然变得很僵。
The relationship between his mother and him soured suddenly.
造句：
Her plan to enter into a elite school soured after her mother refused to give her any help.