interest的形容词是interested和interesting。

interest

n.兴趣;关注;引人关注的性质;吸引力;趣味;业余爱好;利益

v.使感兴趣;使关注

第三人称单数： interests

复数： interests

By that time I had lost interest in the idea.

那时我已经对此想法失去兴趣了。

She took no interest in the people and things around her.

她对周围的人和事毫无兴趣。

Just out of interest, how much did it cost?

我只是好奇问问，这个花了你多少钱？