Essential Oil Terms Glossary — Complete A–Z Guide to Aromatherapy & Essential Oil Terminology

Essential Oil Terms Glossary — Complete A–Z Guide to Aromatherapy & Essential Oil Terminology

Essential oils and aromatherapy have a precise technical vocabulary that can be confusing for newcomers and experienced users alike. This glossary is your authoritative A–Z reference for essential oil terms, aromatherapy concepts, extraction methods, quality standards, and safety terminology.

A

Absolute
An aromatic extract produced by solvent extraction, typically from delicate flowers (jasmine, rose, tuberose) that cannot withstand steam distillation. Absolutes are highly concentrated and have a richer, more complex aroma than steam-distilled oils. Not recommended for internal use due to potential solvent residues.
Adulteration
The fraudulent addition of synthetic compounds, cheaper oils, or undisclosed substances to an essential oil. Common forms: dilution with carrier oils, synthetic fragrance addition, species substitution, rectification. GC/MS testing is the primary detection method.
Aromatherapy
The therapeutic use of essential oils and aromatic plant extracts to support physical, emotional, and psychological wellbeing. Methods include diffusion, inhalation, topical application (diluted in carrier oil), and bathing.

B

Base Note
Essential oils with the slowest evaporation rate (4–6+ hours), providing depth and fixative properties to a blend. Examples: Sandalwood, Vetiver, Patchouli, Frankincense, Cedarwood.
Botanical Name
The Latin binomial (genus + species) that uniquely identifies a plant species. Always check the botanical name on essential oil labels to prevent species confusion. Example: Lavandula angustifolia (true lavender) vs. Lavandula x intermedia (lavandin).

C

Carrier Oil
A fixed (non-volatile) vegetable oil used to dilute essential oils for safe topical application. Common carrier oils: coconut, sesame, jojoba, sweet almond, rosehip.
Chemotype (CT)
A botanical variety of a plant species that produces a significantly different chemical composition in its essential oil despite being botanically identical. Example: Rosmarinus officinalis CT camphor, CT cineole, and CT verbenone — three chemotypes with different therapeutic properties.
CO2 Extraction
An extraction method using supercritical carbon dioxide as a solvent at low temperatures. CO2 extracts capture a more complete range of aromatic and therapeutic compounds without heat degradation — considered superior to steam distillation for many plants.
Cold Pressing (Expression)
A mechanical extraction method used for citrus essential oils (lemon, orange, bergamot, lime). The peel is mechanically pressed without heat. Cold-pressed citrus oils are photosensitising — avoid sun exposure after topical application.

D

Dermal Sensitisation
An allergic reaction that develops after repeated skin exposure to a sensitising compound. Once sensitised, even tiny amounts can trigger a reaction. Known sensitisers: clove, cinnamon bark, lemongrass — use at very low dilutions.
Diffusion
The dispersal of essential oil molecules into the air using a diffuser. Limit sessions to 30–60 minutes and ventilate the room. Keep away from pets.
Dilution
Mixing essential oils with a carrier oil to reduce concentration for safe topical application. Standard dilutions: 0.5–1% facial use, 2–3% general body use, up to 5% acute localised use.

E

Enfleurage
A traditional extraction method where delicate flowers are placed on fat-coated glass plates, allowing the fat to absorb aromatic compounds. Extremely labour-intensive and now rarely used commercially.
Essential Oil
A volatile aromatic liquid extracted from plant material through distillation or cold pressing. Essential oils evaporate quickly at room temperature and carry the characteristic fragrance and therapeutic properties of the plant.

F

FCF (Furanocoumarin-Free)
A designation for citrus essential oils (particularly bergamot) from which photosensitising furanocoumarins have been removed. FCF bergamot can be used in skin care without photosensitisation risk.
Fixed Oil
A non-volatile vegetable oil (carrier oil) that does not evaporate at room temperature. Distinguished from essential oils (volatile oils). Examples: coconut oil, sesame oil, jojoba oil.
Fragrance Oil
A synthetic or semi-synthetic aromatic compound designed to mimic natural scents. Fragrance oils have no therapeutic value. Not to be confused with genuine essential oils.

G

GC/MS (Gas Chromatography/Mass Spectrometry)
The gold standard analytical method for verifying essential oil chemical composition and detecting adulteration. GC separates individual compounds; MS identifies each compound. A GC/MS report confirms authenticity and chemical profile.

H

Hydrodistillation
An extraction method where plant material is submerged in water and boiled. Used for roots, seeds, and hard plant material that benefits from direct water contact.
Hydrosol
Also called floral water or hydrolat — the aromatic water produced as a by-product of steam distillation. Much gentler than essential oils; can be used directly on skin without dilution. Examples: rose water, vetiver water, lavender water.

L

Lavandin
A hybrid lavender (Lavandula x intermedia) with higher camphor content, stronger aroma, and lower therapeutic quality than true lavender (Lavandula angustifolia). Widely used in cleaning products. Always check the botanical name.

M

Middle Note
Essential oils with a medium evaporation rate (2–4 hours), forming the heart of a blend. Examples: Lavender, Geranium, Rosemary, Cardamom, Clary Sage.
MSDS / SDS
Material Safety Data Sheet / Safety Data Sheet — a document providing detailed information about a substance's properties, hazards, safe handling, and storage. Required for essential oil exports and professional use.

N

Neat Application
Applying undiluted essential oil directly to skin. Generally not recommended — most oils require dilution. A few oils (lavender, tea tree) are sometimes used neat in small amounts for specific applications.

O

Oxidation
Chemical degradation of essential oils through exposure to oxygen, light, and heat. Oxidised oils lose therapeutic potency and can become skin sensitisers. Store in dark glass, tightly capped, away from heat and light.

P

Patch Test
A safety test before using a new essential oil topically. Dilute to 1% in carrier oil, apply to inner forearm, leave 24 hours, check for redness or irritation before full use.
Photosensitisation
A reaction where certain compounds (particularly furanocoumarins in citrus oils) react with UV light to cause skin darkening or burning. Avoid sun exposure 12–24 hours after applying photosensitising oils. Affected oils: bergamot, lemon, lime, grapefruit.

R

Rectification
A redistillation process used to remove or concentrate specific compounds. Rectified oils have an altered chemical profile. A form of adulteration when undisclosed.

S

Shelf Life
The period during which an essential oil retains therapeutic potency and safety. Most oils: 1–3 years. Citrus oils: 6–12 months. Base note oils (sandalwood, vetiver, patchouli): 5+ years.
Steam Distillation
The most widely used essential oil extraction method. Steam passes through plant material, carrying volatile aromatic compounds into a condenser where they cool and separate from the water. The gold standard for most herbs, flowers, leaves, and bark.

T

Therapeutic Grade
A marketing term — there is no official regulatory standard or certification for "therapeutic grade" essential oils. Best quality indicators: GC/MS testing, botanical name, country of origin, extraction method, and supplier transparency.
Top Note
Essential oils with the fastest evaporation rate (1–2 hours), providing the first impression of a blend. Examples: Lemon, Bergamot, Peppermint, Eucalyptus, Grapefruit.

V

Volatile
The property of evaporating quickly at room temperature. Essential oils are volatile — they evaporate and disperse into the air. Distinguished from fixed (carrier) oils which are non-volatile.

Related Resources from Blueberry Botanicals

Regulatory Compliance

This content complies with: Drugs and Magic Remedies (Objectionable Advertisements) Act, 1954 · Advertising Standards Council of India (ASCI) Guidelines · Google Global Healthcare & Medicines Policy.

Last Updated: July 2026 | Maintained by: Blueberry Botanicals Content Team | Classification: Public Glossary | Status: Active