The precise definition of Essential Oils will vary depending on who one is speaking to. The most basic Essential Oil definition is that they are the concentrated volatile aroma compounds found in plant materials including flowers, leaves, seeds, berries, peels, needles, twigs, bark, wood, roots, resin, etc. Plants produce them for a number of reasons. Some Essential Oils may attract animals that pollinate or disperse seeds while others may function to repel or poison animals that threaten the plant. Essential Oils may also play a role in the hormonal cycle of plants as well as being components of a plant’s immune system.
In the natural products industry the term “Essential Oil” is generally reserved for those oils that have been either steam distilled or cold pressed, which includes the vast majority of oils on the market. Oils that have been solvent extracted are generally referred to as Concretes and Absolutes and are considered by many to be entirely distinct from Essential Oils, although still many others consider the distinction arbitrary. Similarly, carbon dioxide extracted oils may or may not be considered Essential Oils depending on who one is talking to.