There are many ways to group essential oils or to classify them so that their functions and properties are easier to understand. Many different courses and books classify them according to one of the following techniques:
It is possible to group essential oils by their botanical classification or by the families they belong to. This method is used in some books, but is very difficult to understand unless you have studied aromatherapy for a long time or if you are a botanist.
Essential oils may be grouped by their therapeutic effects. Any list that shows ailments or complaints and then tells you what oils are good for those problems is listing essential oils therapeutically.
Essential oils can be grouped and listed alphabetically. This is a really easy and quick way to look up specific essential oils and determine everything about them.
Essential oils can also be grouped together according to their chemical constituents. This is very uncommon and is usually only used by those advanced in aromatherapy.
Escents Aromatherapy categorizes Aroma Blends in mood categories depending on the mood the oil helps to create.