The Nail Glossary: Every Term Explained

Every nail term you are likely to meet, in plain English. 33 definitions covering products and techniques, the parts of the nail itself, the ingredients worth knowing about, and the words for things going wrong. Written because the category is full of brand names used as generic terms, which makes comparing anything unnecessarily hard.

Jump to: Products and techniques · Nail anatomy · Ingredients and safety · Application and problems

Products and techniques

Semi-cured gel strip: Real gel polish cured to around 80 per cent during manufacture, so it arrives as a flexible strip. You press it on and finish the cure under a UV or LED lamp in about 60 seconds.
Nail polish strip: Real nail polish in a dry, flexible strip. No lamp and no drying time, applied by pressing on and filing off the excess. Sometimes called a nail wrap or a polish sticker.
Gel polish: Liquid gel colour painted on and cured under a lamp, usually in a salon. Wears two to three weeks and is removed by soaking in acetone.
Shellac: A brand of gel polish, used colloquially to mean any salon gel manicure, in the way Hoover came to mean vacuum cleaner.
BIAB: Builder in a bottle. A thicker builder gel applied over the natural nail to add structure, lasting three to four weeks. An overlay rather than an extension, though often used beneath one.
Acrylic: A liquid monomer and powder polymer mixed and shaped on the nail, used mainly for extensions. Hard-wearing, removed by soaking and filing.
Dip powder: Coloured powder sealed onto the nail with resin rather than cured under a lamp. Lasts three to four weeks and is removed with acetone.
Press-on nails: Pre-formed plastic nails attached with adhesive tabs or glue. They sit on top of the nail rather than following it, and can add length.
Overlay: Any product applied over the natural nail for strength or colour without adding length.
Extension: Any technique that makes the nail longer than it grows, using a tip or a sculpting form. Not achievable with strips.

Nail anatomy

Nail plate: The hard visible part of the nail. It is made of dead keratin in bonded layers, which is why it cannot heal and why damage has to grow out.
Nail bed: The living skin beneath the nail plate. Its blood supply is what gives a healthy nail its pink colour.
Free edge: The part of the nail that has grown past the fingertip. Where filing happens and where peeling usually starts.
Cuticle: The thin layer of skin at the base of the nail that seals the gap between skin and nail plate. Best pushed back gently and oiled rather than cut.
Eponychium: The living fold of skin at the base of the nail, often confused with the cuticle. This one should never be cut, because it seals the nail from infection.
Sidewall: The groove where the nail plate meets the skin at each side. A strip that touches the sidewall will lift, which is why sizing down is the rule.
Lunula: The pale half-moon at the base of the nail, most visible on thumbs. Part of the nail matrix showing through.
Nail matrix: The tissue under the base of the nail where new nail is produced. Damage here, unlike damage to the plate, can affect how the nail grows.

Ingredients and safety

HEMA: Hydroxyethyl methacrylate, a common gel ingredient and a known contact allergen. HEMA-free formulations exist for people who react to it. Velvora gel strips are HEMA free.
TPO: Trimethylbenzoyl diphenylphosphine oxide, a photoinitiator that helps gel cure under a lamp. Restricted in EU cosmetics from September 2025. Velvora gel strips are TPO free.
Photoinitiator: The ingredient that reacts to UV or LED light and triggers curing. Without one, gel would stay liquid under a lamp.
Cruelty free: Not tested on animals at any stage. Distinct from vegan, which is about whether animal-derived ingredients are used.
Acetone: A strong solvent used to dissolve gel, acrylic and dip products. Effective but drying, and repeated use is the main cause of thin, brittle nails.
Non-acetone remover: A gentler solvent that removes ordinary polish and polish strips. Slower on gel, kinder to the nail plate.

Application and problems

Curing: Hardening gel under UV or LED light. A semi-cured strip needs roughly 60 seconds to finish curing.
Heat spike: A brief burning sensation during curing, caused by the heat that the curing reaction releases. Thicker layers on thinner nails produce more of it. Removing your hand for a second and returning it spreads the cure.
Lifting: When an edge of the product separates from the nail. Usually starts at the cuticle or sidewall, and usually traced to moisture, oil or an oversized strip.
Delamination: The layers of the nail plate separating, seen as papery peeling at the tip. Driven by repeated wetting and drying, and by solvent exposure.
Wrinkling: Ripples in a strip after application, caused by stretching it during placement or pressing from the wrong direction.
Flooding: Getting product onto the skin around the nail. It has nothing to bond to there, so it lifts early and takes the edge with it.
Nail prep: Cleaning, drying and dehydrating the nail before application. The single largest factor in how long any manicure lasts.
Beau lines: Horizontal grooves across the nail marking an interruption in growth. Unlike the common vertical ridges, recurring Beau lines are worth showing to a GP.
Onycholysis: The nail plate separating from the nail bed, usually appearing as a white or opaque area. A medical matter rather than a beauty one.

Still stuck on a term? The FAQ page covers the practical questions, and the guides hub has the how-to material. If something is missing here, tell us through the contact page and we will add it.