There have been various attempts over the years to break down the world of fragrance into classifiable categories. While there is no unchallenged standard, the often cited 7-category system used by the SociTtT Frantaise des Parfumeurs is as follows: citrus, floral, fougere, chypre, woody, amber and leather. Conversely, Michael Edwards' Fragrances of the World uses a wheel of 4 categories: fresh, floral, oriental and woody. In either system, there are multiple subcategories of further specificity. Other versions may use overlapping terms from both. As there is no universal system, it is common to see a single fragrance categorized in multiple conflicting (or non-conflicting) ways, which is why it's best to use the families as loose guidelines and not rely on them too heavily.