ME Cosmetology key terms

The middle and thickest layer of a hair strand, made of elongated keratinized cells. It holds melanin, gives hair its strength and elasticity, and is the layer changed by coloring, perming, and relaxing.

The tough, transparent outer layer of overlapping scales that protects the hair shaft. It must be lifted or opened for color and waving lotions to enter, and damage to it causes porosity and loss of shine.

The innermost core of the hair shaft, a row of cells that may be absent in fine or light-colored hair. It has little role in styling or chemical services and is not a target of salon treatments.

The ability of hair to absorb and retain moisture, determined by the condition of the cuticle. Low porosity resists absorption; high porosity absorbs quickly but loses moisture and color fast.

The ability of wet hair to stretch and return to its original length without breaking. Normal hair stretches about half its length; poor elasticity signals damage and limits chemical services.

The active growth stage of the hair cycle, when cells divide at the follicle and the hair lengthens. It lasts several years and determines how long hair can grow before shedding.

The resting stage of the hair cycle, when growth stops and the hair is held in the follicle before shedding. It lasts a few months and is followed by new growth and shedding.

The tube-shaped pocket in the skin from which hair grows, containing the root, bulb, and sebaceous gland. Its shape and size determine hair texture and whether hair is straight, wavy, or curly.

The amount of pull applied to hair during blow-drying, thermal styling, or wrapping. Even, moderate tension smooths the cuticle; excessive tension can break hair or damage the scalp.

Shaping hair with heat tools such as blow-dryers, curling irons, flat irons, and hot rollers. Heat temporarily breaks hydrogen bonds, so the shape holds until moisture or new heat resets it.

A weak, temporary bond in hair that is broken by water or heat and re-forms as hair dries or cools. Wet setting and thermal styling rely on these bonds to hold a new shape.

A strong chemical bond between sulfur atoms in the cortex that gives hair permanent shape. It is broken by waving lotion or relaxer and re-formed by neutralizer or oxidation to lock in the new curl or straightness.

Dividing hair into clean, controlled subsections before cutting, coloring, or styling. Consistent partings allow even application and balanced results, and are the base of every precision haircut.

The angle at which hair is held away from the head while cutting, also called projection. It controls the length relationship between layers and creates graduation, uniform layers, or long layers.

The first cut section of a haircut that sets the length and shape for all following sections. It may be stationary for a solid line or traveling for layered and graduated forms.

A haircut in which hair is cut at one length with zero elevation, producing a solid, heavy perimeter line. It requires precise sectioning and is the foundation for one-length styles.

A hydrogen peroxide solution that opens the hair cuticle and starts the oxidation reaction in permanent color and lighteners. Its volume strength controls the amount of lift and deposit.

A small skin test of a color or chemical product applied before a service to detect an allergic reaction. It is required before aniline-derivative tints and is documented in the client record.

A test on a small cutting of the client's hair to predict how a color, lightener, or relaxer will act. It checks timing, lift, and condition before the full service is performed.

An oxidative dye that enters the cortex and permanently changes hair color. It provides lift, deposit, or gray coverage and requires a developer and a patch test.

A strong alkaline product, usually sodium hydroxide or guanidine hydroxide, that breaks disulfide bonds to straighten curly or textured hair. It requires careful timing, base protection, and a neutralizer.

A product applied after a perm or relaxer to rebuild disulfide bonds and stop the chemical action. It restores the hair's strength and sets the new curl or straight shape.

A six-point classification of skin type based on how skin responds to ultraviolet light, from very fair to deeply pigmented. Estheticians use it to plan treatments and sun protection.

Removing dirt, oil, and makeup from the skin with a product suited to the client's skin type. It is the first step of every facial and prepares skin for further products.

Removing dead cells from the skin surface by mechanical or chemical means. It improves texture and product absorption, but must be avoided on irritated or recently waxed skin.

A condition that makes a service unsafe or inadvisable, such as broken skin, infection, or an allergic reaction. The practitioner must recognize it and refer the client rather than proceed.

Reducing the number of pathogens on tools and surfaces to a safe level, usually by washing, then disinfecting with an EPA-registered product. It protects clients and staff from cross-contamination.

Destroying most pathogenic microorganisms on hard, nonporous implements using an EPA-registered hospital-grade product. Tools must be cleaned first and fully immersed for the labeled contact time.

Destroying all microbial life, including bacterial spores, usually with an autoclave. It is required for invasive tools and is stronger than disinfection, which spares some spores.

A document supplied with a chemical product that lists its hazards, safe handling, first aid, and storage. Salons must keep current sheets available for every product used.

The visible, hardened keratin structure covering the nail bed. It protects the fingertip, and its surface must be gently prepared before polish or enhancements are applied.

The skin beneath the nail plate, rich in blood vessels and nerves. Damage to it can permanently deform the nail, and it should never be cut or abraded during a manicure.

Any nail disease or disorder, such as thickening, discoloration, or separation. A licensed practitioner may not treat it and must refer the client to a physician.

The study of the structure of the human body and its parts. Cosmetologists need it to locate muscles, bones, and nerves and to work safely around the face, head, and hands.

The study of how body structures function and interact. It explains processes such as circulation, skin renewal, and hair growth that affect services and client safety.

Tissue that contracts to produce movement, such as the frontalis lifting the brow or the masseter closing the jaw. Massage strokes follow muscle direction for comfort and safety.

The legal authorization to practice cosmetology in Maine after meeting education, examination, and application requirements. Practicing without a current license is prohibited and subject to penalty.

The services and activities a licensee is legally permitted to perform under Maine law. Working outside it, such as diagnosing disease or practicing beyond training, can lead to discipline.

Required training hours a licensee completes during each renewal period to keep a Maine license active. Records must be kept and made available if requested by the licensing authority.

A written or electronic file of services, products, test results, and client information. Maine rules require accurate records, and they support safe repeat services and defensible documentation.