成功的定义难以捉摸，每个人对它的理解都不一样。

The ___elusiveness of success means everyone defines it differently.

那只野兔凭借其难以捕捉的特性多次逃脱了猎人的追捕。

The hare's ___elusiveness allowed it to escape the hunter's pursuit multiple times.

数学概念的难以捉摸让许多学生感到困惑。

The ___elusiveness of mathematical concepts confuses many students.