idea/ aɪ'dɪə /

1.noun [c] 
(scheme) 主意

I had a brilliant idea.
我有个绝妙主意。
2.noun [c] 
(opinion,theory) 看法

People had some odd ideas about us.
人们对我们有些古怪的看法。
3.noun [c/u] 
(notion) 概念

Do you have any idea how big the project is going to be?
你对项目规模有概念吗?
Have you any idea how much it would cost?
你知道大概是多少钱吗?
4.noun [s] 
(objective) 目的

The idea is to try and avoid further expense.
目的是尽量避免更多的开销。
once you get the idea
一旦你明白了
(what a) good idea!
(真是个)好主意!
to have a good/clear idea of sth
非常了解某事
I haven't the slightest {or} faintest idea
我根本就不知道
that's not my idea of fun
那不是我的兴趣所在