what is the difference between a semi permeable and a differentially permeable membrane?

I mainly used semi-permeable

Semi permeable - means partially permeable, and will only let smaller molecules through
differentially permeable - means permeable to certain molecules only - this could be based on size, charge, shape or any other factor that affects movement.

Hence I would say, just from the words alone that things that are semi-permeable are just differentially permeable ACCORDING TO SIZE. Whereas differentially permeable doesn't have to be according to size, but rather to anything causing the difference in permeability.

For example:
Intestine wall is semi-permeable (water + few small molecules/ions)
Kidney wall is differentially permeable (according to ionic charge)

Those terms can be used interchangeably.  Since there is a "difference" in what goes through and what doesn't,  I prefer to use the term "differentially."