Herbalism ('herbology' or 'herbal medicine') is the use of plants for medicinal purposes, and the study of such use. It covers all sorts of medicinal plants, natural remedies or cures, traditional and alternative medicines. Modern medicine tends to categorise herbalism firmly as an 'alternative therapy' as its practice is not strictly based on evidence gathered using the scientific method. Modern medicine does make use of many plant-derived compounds however, as the basis for evidence-tested pharmaceutical drugs. Phytotherapy also works to apply modern standards of effectiveness testing to medicines derived from natural sources