MO Cosmetology key terms

A 0-to-14 measure of how acidic or alkaline a water-based solution is, with 7 neutral; hair and skin products are formulated to work within specific ranges on it.

The middle layer of a hair strand, made of elongated keratinized cells; it holds pigment, moisture, and the disulfide bonds that give hair strength and shape.

The tough, overlapping outer layer of a hair strand that protects the cortex; it lifts in alkaline solutions and closes in acidic ones, controlling porosity and shine.

A strong chemical link between sulfur atoms in neighboring keratin chains; these bonds are broken by waving and relaxing products and re-formed in the new shape during processing.

The ability of hair to absorb and hold moisture, rated low, normal, or high; overly porous hair takes color fast but loses it quickly and needs gentler chemical service.

The property that lets wet hair stretch and return to its original length; poor elasticity signals damage and warns against strong chemical services.

The direction in which hair leaves the scalp, including cowlicks and whorls; it determines where partings and lines fall and how much tension a cut requires.

A section of hair that grows in a direction opposite to the surrounding hair, often at the hairline; it resists styling and must be directed deliberately when cutting.

A shampoo formulated near the natural pH of hair and scalp, which minimizes cuticle swelling and helps preserve color and moisture between services.

A stronger detergent shampoo that removes product buildup, minerals, and oils; it can strip color and dry the scalp, so it is used sparingly and with conditioning afterward.

A product applied after shampooing to smooth the cuticle, restore moisture, reduce static, and improve combability; types include rinse-out, leave-in, and deep treatments.

Examination of the scalp for redness, flakes, lesions, oiliness, or parasites before a service; abnormal findings are referred out rather than treated in the salon.

A condition that makes a service inadvisable or unsafe, such as open sores, contagious scalp disease, or irritated skin; the professional declines or postpones the service.

The angle at which hair is held away from the head while cutting, measured from the scalp; it controls the amount of graduation or layering built into the shape.

The first section of hair cut in a shape, establishing the length and line that subsequent sections follow; it may be stationary or moving.

A cutting technique in which hair lengths build up in layers, creating a stacked or wedge effect; it is produced by cutting at an elevation lower than the previous section.

Re-cutting a section from the opposite direction to verify balance and evenness; it catches mistakes that a single cutting position can hide.

A small application of a chemical product on skin, usually behind the ear or in the elbow crease, observed for a reaction before a full service; results are documented.

The family of permanent oxidative hair colors that require a developer and a patch test; they lift and deposit color inside the cortex and cannot be shampooed out.

A hydrogen peroxide solution that, when mixed with oxidative color or lightener, supplies oxygen to develop color and to lighten natural pigment; its strength is stated in volumes.

Processing a small cutting of the client's hair with the intended formula to preview timing, color result, and condition before applying product to the whole head.

A product, usually sodium hydroxide or a no-lye alternative such as guanidine, that breaks disulfide bonds to straighten curly or resistant hair; it requires a base and careful timing.

A service that permanently straightens hair by applying a strong alkaline product, then rinsing and neutralizing to rebuild bonds in the straightened shape.

A permanent wave product, typically ammonium thioglycolate, that softens and opens the cuticle to reshape hair; it is followed by a neutralizer that re-forms the bonds.

The visible, hardened keratin structure covering the nail bed; its condition, shape, and surface are assessed before manicuring or applying enhancements.

The living tissue at the base of the nail where new cells form and keratinize; injury or disease here permanently affects the growing nail plate.

A structural or health abnormality of the nail such as pitting, ridges, or discoloration; a cosmetologist may not diagnose or treat it and refers the client to a physician.

A six-category classification of skin tone and its typical response to ultraviolet exposure, used to judge sun sensitivity and select safe treatment intensity.

Removing dirt, oil, and product from the skin with a suitable cleanser as the first step of a facial; it prepares the skin for analysis and treatment.

Destroying most pathogenic microorganisms on nonporous implements and surfaces with an EPA-registered hospital-grade disinfectant, following label contact time.

Destroying all microbial life, including spores, usually by autoclave or dry heat; required for implements that may contact blood or broken skin.

Lowering the number of microorganisms on surfaces and linens through washing and cleaning; it is the basic hygiene step that precedes disinfection.

A porous or disposable implement, such as a paper file or wooden stick, that cannot be safely disinfected and must be discarded after one client.

Reusable tools such as shears, combs, and clippers; nonporous implements are cleaned, then immersed in disinfectant between clients, and porous ones are discarded.

The periodic process by which a Missouri licensee keeps an active credential by meeting continuing education and fee requirements before the expiration date.

Required hours of approved instruction a Missouri licensee completes within each renewal cycle to maintain the license and stay current in practice.

The services and procedures a Missouri cosmetologist is legally trained and licensed to perform; working outside it can bring discipline against the license.