unable vs. not able

[sb70012]

Hello dear all,

As you know, the negative form of able is unable. Can we also use not able instead of unable or not?

For example:

I am unable to understand what she wants.
I am not able to understand what she wants.

Is the second sentence correct or not? (I men not able)

Thank you.

 

[Rover_KE]

They are both correct and have the same meaning.