I think that the difference is that a semi-permeable allows only certain things to pass through which are those that are small enough while permeable again i say i think allows almost all things to pass through
Semi-permeable. They let some things in, and others out. Typically, nutrients and water are let in, and waste products from cellular metabolism are let out!
the differences is that semi- permeable only lets in and out molecules small enough to fit threw period selectively permeable has channel proteins that allow bigger molecules to fit threw.