Glossary

Skin & undertone

Undertone: The underlying warmth or coolness of skin, independent of how light or dark it is. See Color Matching & Undertones.
Cool, warm, and neutral tone: The three broad undertone categories: cool skin has pink or blue undertones, warm skin has yellow or golden undertones, and neutral skin is a mix of both. See Color Matching & Undertones.
Combination skin: A skin type that's oily in some areas (usually the T-zone) and normal or dry in others, which often means one finish or formula doesn't work well across the whole face. See Foundation for Combination Skin.
T-zone: The forehead, nose, and chin, which together form a T shape and tend to produce more oil than the rest of the face.
Sebum: The natural oil produced by skin's sebaceous glands. Higher sebum production is what makes skin read as "oily" and can cause makeup to slide or fade faster.

Formula & ingredients

Comedogenic / non-comedogenic: Comedogenic describes an ingredient or product likely to clog pores and contribute to breakouts; non-comedogenic products are formulated to avoid this, which matters most for acne-prone skin.
Silicone-based formula: A formula built on silicone (often listed as dimethicone), which blurs texture and creates a smooth, long-wearing finish. See Primer.
Water-based formula: A formula built on water rather than oil or silicone, which tends to sit thinner on skin and feel more breathable. See Foundation.
Talc-free: A powder formula that replaces talc with alternative bulking ingredients such as mica or starches, marketed mainly on ingredient preference rather than a meaningful performance difference. See Powder.
Fragrance-free: A product formulated without added fragrance ingredients, relevant for people with fragrance sensitivities - not the same as "unscented," which can still contain masking fragrance.
Hypoallergenic: A marketing term meaning a product is formulated to reduce the likelihood of an allergic reaction. It isn't a regulated or tested guarantee, so it's not a substitute for checking the ingredient list against known sensitivities.
SPF / PA rating: SPF measures protection against UVB rays (the ones that burn); PA, used mainly outside the US, measures UVA protection (the ones linked to aging and deeper skin damage). A product needs both to be broad-spectrum.

Finish & texture

Finish: How a product looks on skin once set: matte (no shine), satin (soft, low sheen), or dewy/glowy (reflective).
Matte: A finish with no shine or reflectiveness, generally favored on oilier skin or in humid climates because it resists looking shiny as the day goes on. See Powder.
Satin: A finish between matte and dewy - a soft, low sheen rather than flat or reflective. Often the easiest finish to wear across different skin types.
Dewy / glowy: A reflective, luminous finish that mimics naturally healthy, hydrated skin. Shows texture more readily than matte finishes. See Highlighter.
Cakey: A flat, heavy, powdery look caused by applying too much product, layering powder over powder, or using a formula that doesn't suit the skin underneath. See Why does powder look cakey or ashy?
Long-wear: A formula engineered to resist fading, smudging, or transferring for an extended period, usually via film-forming or silicone-heavy ingredients. See Setting Spray.
Transfer-resistant: A formula that dries down enough that it doesn't rub off onto skin, fabric, or a mask - common in long-wear lip products. See Lipstick.

Coverage & application

Coverage: How much a product conceals what's underneath it - sheer, medium, or full - determined mainly by pigment concentration.
Buildable coverage: A formula designed to be layered - sheer with one pass, more concealing with two or three - rather than a single fixed coverage level. See Foundation.
Pigment load: How concentrated the color pigment is in a formula. Higher pigment load means more payoff per swipe and often a shorter blending window. See Eyeshadow.
Blending: Softening the edge between two areas of product so the transition reads as skin rather than a visible line. See Blending Basics.
Stippling: A bouncing, dabbing application motion (rather than dragging or wiping) used with sponges and some brushes to deposit product without disturbing layers underneath.
Baking: Pressing a heavy layer of loose powder onto concealer or foundation and leaving it to set for several minutes before dusting off, used to lock in coverage and prevent creasing in a targeted area.
Strobing: Applying highlighter to the face's high points to create light-reflecting glow, as a lighter alternative to full contouring. See Highlighter.
Draping: Sweeping blush up and along the cheekbone toward the temple, rather than just on the apple of the cheek, to add both color and soft shape. See Blush.
Setting: Applying a translucent or tinted powder over liquid or cream products to reduce shine and help them last longer.
Waterline: The strip of wet skin just above the lower lash line, between the lashes and the eye itself - a common place to apply liner for a more intense eye look. See Eyeliner.
Tightline: Applying eyeliner into the upper lash line itself, between the lashes rather than above them, to make lashes look fuller without a visible line. See Eyeliner.

Color correcting

Color corrector: A concealer that uses an opposing hue (e.g. peach over blue-purple) to neutralize discoloration before a skin-matched concealer is applied.
Peach corrector: A warm peach or orange corrector used to neutralize blue or purple tones, most often under-eye darkness. See Color Correctors.
Green corrector: A green-toned corrector used to neutralize redness, such as active blemishes or rosacea flare-ups. See Color Correctors.
Lavender corrector: A light purple corrector used to counteract sallow, yellow-toned dullness, most often on fair skin. See Color Correctors.
Yellow corrector: A yellow-toned corrector used to neutralize purple or blue-purple discoloration, such as bruising or deeper under-eye darkness on medium-to-deep skin. See Color Correctors.
Concealer triangle: An inverted-triangle placement of concealer under the eye, wider near the inner corner and tapering toward the cheek, used to brighten rather than just cover the darkest spot. See Concealer.

Common problems

Oxidization: A color shift, usually darker or more orange, that happens as a formula reacts with air and skin oils after application. See Why does foundation oxidize and turn orange?
Fallout: Loose pigment, usually from powder eyeshadow, that drops onto the under-eye area or cheeks during application. See Why does eyeshadow fall out under the eyes?
Creasing: Product settling into fine lines or folds of skin, most visible under the eyes, as it moves throughout the day. See Why does concealer crease under the eyes?
Flashback: A white or gray cast that appears in photos taken with flash, most often caused by SPF minerals (zinc oxide, titanium dioxide) or silica in powder reflecting the flash back at the camera rather than absorbing it the way skin does.

Techniques & looks

Cut crease: An eyeshadow technique that keeps a sharp, undisturbed line at the crease to make the eyelid read as a distinct shape. See Cut Crease.
Halo eye: An eyeshadow placement that concentrates the darkest color in the center of the lid and blends outward, brightening the inner and outer corners for an opened-up effect.
Contouring: Using a shadow-toned product to create the illusion of depth or shadow on the face, typically along the jaw, temples, and under the cheekbone. See Contouring & Highlighting.
Highlighting: Using a lighter or reflective product on the face's high points to draw light forward and add dimension opposite to contouring. See Contouring & Highlighting.