Roy knew what that word meant. But he looked the potion up anyway. The description said "This potion turns the drinker into their male or female counterpart. Drinking some again will turn them back to their original state. Multiple use has the same effect regardless of how many times it has been used. Everyone around the drinker will think they had always been that way."
Roy knew that almost every boy dreamed of knowing what it was like to have a full set of girl parts. He was not one of the few who was different. He got undressed and closed his door so he could watch the transformation. He popped the top off and drank it. Like the letter had said, the bottle stayed full. But nothing else happened. He should have known it was some sort of prank. Then he got a funny feeling in his crotch. He looked down to see his genitals shrinking. Then they disappeared altogether as they were sucked inside his body, replaced by a vagina. Being a genius in school, he knew that the shifting feeling inside his stomach was undoubtedly the rearrangement of his internal organs so that he had ovarian tubes, a not yet fully developed uterus, and the disappearance of his testes. Then two small breasts appeared and his arms and legs thinned and altogether lost their masculinity. Then he, or she, looked in a mirror to watch his face become feminine and the lengthening and lightening of her hair to a blondish color.
Roy reached down to feel her vagina and clitoris. Roy was now Rhonda.