MT Cosmetology key terms

The slightly acidic film of sebum and sweat on the skin's surface, around pH 4.5 to 5.5, that discourages bacteria and helps the skin retain moisture.

The active growth stage of a hair follicle, lasting roughly two to seven years, during which new cells are added at the bulb and the hair lengthens.

A tiny involuntary muscle attached to each hair follicle that contracts in cold or emotion, lifting the hair and producing goose bumps on the skin.

A protective lotion applied to the hands or face before a service to limit contact with water, shampoo, and chemicals, making cleanup easier and reducing irritation.

In hair coloring, the underlying warm or cool tone the natural pigment contributes at a given level, used to predict how a tint will look and how it will fade.

A haircut in which all strands are cut at one length along a single line, producing a solid, heavy perimeter with no visible layering.

The short transitional stage of the hair growth cycle, lasting a few weeks, when growth stops and the follicle begins to shrink and detach from the bulb.

The thick middle layer of a hair strand, made of elongated keratinized cells, that holds the melanin and gives hair its strength, elasticity, and curl.

Cutting a section of hair at a second angle, usually perpendicular to the first cut, to verify that the line is even and no strands were missed.

The tough outer layer of overlapping, scale-like cells on a hair strand; when it lies flat hair looks shiny, and when it lifts hair feels rough and loses moisture.

A hydrogen peroxide solution mixed with hair color or lightener to open the cuticle, oxidize pigment, and deposit or remove color at a chosen strength and speed.

The use of an EPA-registered hospital-grade product on hard, nonporous implements to destroy most pathogenic microorganisms, except bacterial spores, after cleaning.

The angle at which a subsection of hair is held away from the head before cutting, which determines whether the resulting shape is layered, graduated, or solid.

A cutting technique in which hair is held at a low elevation and cut shorter at the nape, creating a stacked or wedge-shaped build-up of weight.

The rounded, enlarged base of a hair follicle that surrounds the papilla and contains the actively dividing cells that produce the hair shaft.

A tube-shaped pocket in the dermis from which a hair grows, containing the bulb, root, and sebaceous gland, and extending from the surface to the subcutaneous layer.

A number on a scale from 1 (black) to 10 (lightest blonde) describing how light or dark a hair color is, independent of its warm or cool tone.

The skin seal beneath the free edge of a nail where the nail plate separates from the fingertip, an area that traps debris and resists infection.

Any tool used during a service, classified as single-use (disposed after one client) or reusable (cleaned and disinfected between clients).

The whitish, half-moon-shaped area at the base of a nail plate, visible where the underlying matrix is thickest and least transparent.

A document supplied by a product manufacturer that lists a chemical's hazards, safe handling, first-aid measures, and spill procedures; it must be kept accessible in the salon.

The living, actively dividing area of tissue at the base of the nail bed that produces the nail plate cells and determines the nail's thickness and shape.

The innermost, spongy core of a hair strand, made of loosely packed cells; it may be absent in fine or naturally light hair and plays little role in services.

The pinkish tissue on which the nail plate rests, rich in blood vessels, extending from the matrix to the hyponychium and giving the nail its healthy color.

The visible, hard, translucent portion of a nail made of compacted keratinized cells, protecting the sensitive nail bed beneath it.

Workplace contact with chemicals, dusts, or bloodborne pathogens during services; salons limit it through ventilation, gloves, safe work practices, and written exposure-control plans.

A small application of a color or chemical product on the skin, usually behind the ear or in the elbow crease, checked 24 to 48 hours later to detect an allergic reaction.

A scale from 0 to 14 measuring acidity and alkalinity; hair and skin are mildly acidic, and alkaline products such as relaxers and lighteners swell the cuticle.

A strongly alkaline cream or lotion, usually containing sodium hydroxide or a no-lye agent, that breaks disulfide bonds in the cortex to straighten curly or wavy hair.

The basic, everyday practice of washing hands and cleaning surfaces and tools with soap and water to reduce visible soil and lower microorganism counts.

Oil glands attached to hair follicles that secrete sebum onto the skin and hair, lubricating both and helping form the acid mantle.

The outermost layer of the epidermis, composed of flat, dead, keratin-filled cells that shed continuously and form the skin's main barrier.

A process that destroys all microbial life, including bacterial spores, typically using an autoclave with steam under pressure; not required for most salon implements.

The resting stage of the hair growth cycle, lasting about three months, at the end of which the old hair is shed and a new one begins to grow.

Cutting or thinning techniques that remove weight or create shorter pieces within a shape, adding movement, lift, or a softer edge to the finished style.

A mild, deposit-only color applied after lightening to neutralize unwanted warmth or add a specific tone without significantly changing the hair's level.