概念

1. 这个概念是她的理论的核心。
   This concept is at the very core of her theory.
2. 他对我指的是什么没有一点儿概念。
   He didn't have a slightest notion of what I meant.
3. 掌握无限空间的概念是很难的。
   It is difficult to grasp the concept of infinite space.
4. 这两个概念之间有何联系？
   What is the connection between the two ideas?

念的英语翻译：