Hi Stefano, prevent is to avoid something happening; stop sounds more like it has already started. Be careful with defining sexual abuse - it gets very complicated. I understand you are possibly just giving a simple meaning here. However it involves the fact that there has not been consent; usually a minor (not adult); and not necessarily physical. Note that there is a difference with sexual assault, but that becomes too complicated a discussion for me here. I hope that helps. Simón.