Inevitable is applied to an event or occurrence. If something is inevitable it means that whatever is done to prevent it happening or whatever outside influences are applied it WILL eventually happen. The outside influence may delay it or change the way the occurrence is achieved but it will not prevent it. For example: Regardless of medical advances, death is inevitable. Inexorable is applied to the progress towards an occurrence or event. In this case it means nothing will change the course or speed of the event. For example: Growing old is inexorable.