ABC’s of Essential Oils – Common Terms and Definitions

Essential Oil Terms and Their Meanings


Absolute – An absolute is not an essential oil, but a different type of plant extract. Absolutes are made by chemical extraction or enfleurage. Many companies offer safe absolutes made via CO2 extraction, but it is good to use caution as some maybe distilled with hexane or other less favorable solvents. There is no certainty that other extraction methods are bad, but we prefer caution.

Aromatherapy – the therapeutic use of plant-derived, aromatic essential oils to promote physical and psychological well-being. This may include the use of bottled essential oils, as well as the plants themselves, hydrosols, and other types of extracted essences. The essences may be used alone, in a synergy, or as part of a blend.



Blend – A mix of essential oils and a carrier oil. A blend may be one EO and a carrier, or several essential oils mixed together and diluted in the carrier oil. A mixture of different essential oils with no carrier is called a synergy.

Butter – Fatty oils that are solid at room temperature. These are frequently pressed oils used as carrier oils and for beauty products, such as shea and cocoa. In many recipes, butters can be used almost interchangeably, though each will bring different beneficial components. Does not refer to dairy or nut butters unless specifically noted in a recipe with essential oils.



Carrier Oil (sometimes just “Carrier”) – Any oil used to dilute essential oils. While this can include petroleum-based products like baby oil, it most frequently refers to FCO. Other carrier oils include sweet almond oil, jojoba oil, and castor oil. This term may also be used to refer to butters and waxes, depending on the desired end product.

CO2 Extract – a method of making absolutes, frequently but incorrectly lumped in with essential oils. CO2 extracts and essential oils from the same plants will have different components, so it is important to fully understand which type of extract you have before use. Co2 extracts are quickly breaking in as their own category, separate from essential oils.

Cold Pressed – a type of extraction most frequently used to extract citrus oils. Modern cold-pressed oils are not frequently pressed, but placed in a centrifuge for more complete extraction. In some cases, the oil is made by separating it from the juice as a by-product, which is then filtered further or processed to remove unwanted components as in FCF bergamot. These are still referred to as “cold pressed”. Read more about cold-pressed oils here.



Diffuse (or Diffused) – a method of using essential oils via inhalation. Diffusing oils means dispersing them into the air, by dropping them from the bottle onto various surfaces, or by mechanical methods. This article shows several ways oils may be diffused, both with and without gadgets.

Diffuser – any of a number of styles of devices intended to disperse essential oils into the air. A diffuser may be as simple as a felt pad near your workspace or as complex as an electric atomizing diffuser made of blown glass and hand-carved oak.

Dilution or Dilution Rates – the percentage of an essential oil that should be used in a carrier oil to ensure safety and promote health. In almost all topical and internal applications, essential oils should be diluted, many times heavily.

Drop – generally, an indefinite term meaning nothing more grand than what comes from a dropper bottle or eyedropper. This amount will vary greatly from one oil to another, as more viscous oils will tend to create larger drops than do thinner oils. Manufacturers and medicinal users may have already done calculations before publishing a recipe, or may measure oils by weight when creating products to avoid misuse.

Dropper – this can refer to either a bottle with an orifice reducer, or a separate device such as an eyedropper.



Enfleurage – a process of extracting plant essences into odorless fats, then further breaking down the fat to form an absolute. An old an traditional technique, lard or tallow is infused with the plant’s essences, through either a hot or cold process. Plant matter is added to the fat, and either heater or allowed to rest at room temperature until the fat is infused with the essences. The fat is then washed or soaked with alcohol, to help separate out the essential oils. The alcohol is allowed to evaporate, leaving behind the absolute.

Expeller-pressed – a specific type of cold pressed essential oils. These have been extracted in a centrifuge or other expelling machine.



FCF or “Furanocoumarin Free” – Furanocoumarins, or fourocoumarins, are components existing in many plants that can be toxic or harmful to skin under certain conditions. These components may be destroyed or lessened with heat in the making of essential oil. Some oils that would otherwise contain furanocoumarins are processed after they have been extracted, producing an “FCF” version of the oil. Oils with furanocoumarins are still useful, but are frequently phototoxic.

FCO – “Fractionated Coconut Oil” – coconut oil which has been processed to help it maintain liquidity under ordinary temperatures. Raw coconut oil is more difficult to blend with essential oils, because its state changes from solid to goopy then liquid at common ranges of “room temperature”. FCO is quickly and easily absorbed into skin, making it a commonly-preferred carrier oil when essential oils are used to maintain health.

Food Grade – not used for aromatherapy. Food grade oils are intended for use as natural flavoring in food. The are tested and blended to ensure each tastes or smells the same every time. This may mean the addition of components or similar-tasting oils. If you choose to ingest essential oils as part of aromatherapy or as medicine, these are not the oils you’re looking for. If you’re making and selling candy or baked goods, these may be a good natural flavoring choice.



Grade – no meaning. In the world of aromatherapy and essential oils used for health and wellness, there is no grading of essential oils. Labels like “Therapeutic Grade” or “Grade A” may have no meaning. Other times, the seller or manufacturer uses in-house definitions to let the customer know what they mean when they use the words. See a broader explanation of this phenomenon here.  The exception to this rule is an oil labeled “Food Grade“.



Hot Oils – oils with “skin active” properties. These oils may burn, tingle, or warm, depending on dilution rates and the oil used. Frequently used in topical preparations such as muscle rubs, these oils include cinnamon, wintergreen, lemongrass, black pepper, and cardamom. Dilution of hot oils is important to avoid irritation, more so than usual dilution warnings.

Internal – the use of essential oils when ingested or injected. Injection is for the medical community, and Liberty Zen does not encourage or promote the use of oils by injection. More common is use by ingestion, either as flavoring in food or in a capsule as a home remedy. Internal use of essential oils is hotly debated, and a full description of our position on the topic can be found here.

Liquid Oil – an oil, usually a carrier, that is liquid at room temperature. When a recipe says “any liquid oil”, this does not mean something that can be melted into a liquid, but is solid at room temperature, such as a butter or wax. Common liquid oils include FCO, argan oil, and apricot seed oil. Vitamin E from capsules may also sometimes be substituted.



Made in USA (or other country) – This label indicates where the oil was made, not where the plant was grown. Always look for the origin of the plant as part of your discovery, and to help evaluate the quality of the oil.

MLM (Multi-Level Marketing) – A particular business model using home parties or friend groups to drive sales. A detailed explanation of MLM companies and essential oils can be found here. MLM companies include doTerra and Young Living, along with Avon, Thirty-One, and Tastefully Simple.



Not for Internal Use (Label) – This means only that the company does not intend their oils for internal use. It can be, but is not necessarily, an indication of oil quality. Some oils should never be ingested, and other times this is a label to keep the FDA from determining that the oils are “medical”. While the label may mean business, it is sometimes overkill. It’s important to know your supplier and understand why the label exists. It may be a difference in oils philosophy, it may be that the oil is poison.



Organic – this means that the plants used to make this oil were grown according to USDA organic standards, or the standards of the country where the oil was produced.

Orifice Reducer – a small piece of material, usually plastic, placed in the mouth of a bottle to limit the flow. Orifice reducers are standard with most bottles of essential oils, and may be removed to use an external dropper. Heavier oils and absolutes may be too viscous to use with an orifice reducer.



Pure (label) – little to no meaning. Essential oils may be called “pure” when they contain very little or even none of the oil you think you’re getting. Some companies use this term to mean a product that is 100% of the oil you wish to purchase. It has no official definition in the world of essential oils sales.

Phototoxic – an oil that may cause skin irritation when exposed to sunlight if used topically. Phototoxic oils may cause skin to burn more easily, break out with a rash, or form blisters in the sun. Many common oils are phototoxic, including most citrus. In some cases, the compounds causing the problems may be reduced or removed in an oil; these are frequently labeled “FCF”.



Resin – sticky substance from trees. Resin is exuded when trees are wounded, trapping the volatile essential oils of the tree. Essential oils from tree resins are frequently “distilled” by CO2 extraction, though many can be made by steam distillation as well. Frankincense and myrrh are two of the most commonly-used resin oils in aromatherapy.

Rollerball – a glass bottle with an attachment at the top including a ball that rolls freely to distribute the contents of the bottle. Generally, the attachments will be plastic, but the ball itself made of either metal or plastic. Metal is preferred for use with essential oils as plastic may be broken down and release unwanted chemicals.



Steam Distilled – oils that have been made by heating the plant matter with water and allowing the oils to separate from the resulting steam. The steam is captured and allowed to cool; as it does, the oils separate from the water. This is the most common method of creating essential oils.

Synergy – a mixture of two or more essential oils without a carrier oil. Generally these combinations are intended to work in conjunction with one another for a specific purpose.



Therapeutic – two definitions. “Therapeutic” may be used in an aromatherapy setting to mean an oil with components intended for specific uses within the body. More frequently, it is used with the word “grade“, taking away most or all meaning. Each company or seller may define “therapeutic grade” in their own way.

Topical – the use of essential oils as applied to the skin. Rollerball blends, lotions, and balms are common examples of topical use. Some oils may be used topically outside of a blend, provided other safety measures have been considered.



Wax – a heavily fatty product, solid at room temperature with a crystal structure different and more stable than a butter. Most frequently beeswax or carnauba wax. These may be used to carry essential oils in balms or to help thicken and strengthen creams and lotions.

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