Mattress Glossary: 41 Terms Explained
Mattress brands use a lot of jargon. Here’s what the most common terms actually mean, in plain English.
- All-foam mattress
- A mattress made entirely of foam layers (memory foam, polyfoam and/or latex) with no coils. All-foam beds usually isolate motion well and are often cheaper, but tend to sleep warmer and have softer edges than hybrids.
- Body impression
- A permanent dip that forms where you sleep. Most warranties only cover impressions deeper than a stated depth, often 1 to 1.5 inches, measured with no one on the bed.
- Break-in period
- The first few weeks when a new mattress softens slightly as its materials loosen up. Many brands suggest sleeping on a mattress for about 30 nights before deciding whether to keep it.
- CertiPUR-US
- A certification for polyurethane foams. Certified foams are tested by independent labs for content, emissions and durability, and are made without certain flame retardants, heavy metals and phthalates.
- Coil count
- The number of springs in a mattress, usually quoted for a queen. A higher count can mean more targeted support, but coil design and gauge matter as much as the number.
- Coil gauge
- The thickness of the steel wire used for springs. Lower gauge numbers mean thicker, firmer wire (around 12–13 gauge); higher numbers mean thinner, more flexible wire (around 15–16 gauge). Edge coils are often thicker.
- Combination sleeper
- Someone who changes position through the night, for example from side to back. Combination sleepers usually do best on a medium to medium-firm mattress that is easy to move on.
- Comfort layer
- The top layer or layers under the cover, designed to cushion and relieve pressure. Common materials are memory foam, latex, polyfoam and micro-coils.
- Contouring
- How closely a mattress hugs the shape of your body. Memory foam contours closely; latex and coils contour less and feel more buoyant.
- Density
- How much a foam weighs per cubic foot (PCF). Higher-density foams generally last longer. Density measures durability, not firmness: a dense foam can still feel soft.
- Dunlop latex
- Latex made by pouring liquid latex into a mould in one go. It is usually denser and firmer than Talalay latex, so it is often used in support layers.
- Edge support
- How well the perimeter of a mattress holds up when you sit or lie near the edge. Strong edges make it easier to get in and out of bed and let you use the full surface. Many hybrids reinforce the edges with thicker coils or foam rails.
- Euro top
- A cushioned layer sewn flush with the sides of the mattress (unlike a pillow top, which sits on top as a separate-looking layer). It adds softness and a plush feel.
- Fiberglass-free
- A mattress made without a fiberglass fire barrier. Fiberglass is a common, low-cost way to meet flammability rules; alternatives include wool, rayon blends and silica-treated fabrics. If the cover is opened or torn, fiberglass can escape, so many shoppers prefer beds that avoid it.
- Firmness
- How hard or soft a mattress feels, usually rated on a 1 to 10 scale where 1 is very soft and 10 is very firm. Most people prefer something between 5 and 7. Firmness feels different depending on your body weight.
- Flippable mattress
- A mattress designed to be slept on from either side, often with a different firmness on each side. It lets you change the feel without buying a new bed.
- Foundation
- The base a mattress sits on, such as a platform bed, slatted frame, box spring or adjustable base. Most warranties require a solid or slatted base with slats close together (often 3 inches or less apart).
- GOLS
- Global Organic Latex Standard. Certifies that latex contains at least 95% certified organic raw material and is processed to environmental and social criteria.
- GOTS
- Global Organic Textile Standard. Certifies that textiles such as cotton and wool covers are made with at least 70% (or 95% for the “organic” label) certified organic fibres and meet environmental and social criteria.
- GREENGUARD Gold
- A certification from UL that a product meets strict limits on chemical emissions (volatile organic compounds), designed with sensitive people such as children and older adults in mind.
- Hybrid mattress
- A mattress that combines a coil support core with comfort layers of foam or latex, usually 2 inches or more. Hybrids aim to combine the pressure relief of foam with the bounce, airflow and edge support of springs.
- ILD (Indentation Load Deflection)
- A lab measure of foam firmness: the force in pounds needed to compress a sample by 25%. Higher ILD means firmer foam. You may also see it called IFD.
- Innerspring mattress
- A traditional mattress built mainly on a coil system with only a thin comfort layer on top. Innersprings are bouncy and cool but offer less pressure relief than foam or hybrid beds.
- Latex
- A foam made from the sap of rubber trees (natural latex), synthetic rubber, or a blend. Latex is responsive, durable and naturally sleeps cooler than memory foam. See also Dunlop and Talalay.
- Lumbar support
- Extra support under the lower back. Zoned mattresses put firmer material under the hips and lower back to help keep the spine aligned.
- Memory foam
- A viscoelastic polyurethane foam that softens with body heat and pressure, then slowly returns to shape. It gives a hugging, pressure-relieving feel and isolates motion well, but can trap heat unless it is gel- or copper-infused or open-cell.
- Motion isolation
- How well a mattress stops movement on one side from being felt on the other. All-foam and memory foam beds usually isolate motion best, which matters if you share a bed.
- Off-gassing
- The “new mattress” smell from volatile organic compounds released by foams and adhesives when a mattress is unpacked. It usually fades within a few days in a ventilated room. Certifications such as CertiPUR-US and GREENGUARD Gold limit emissions.
- Phase-change material (PCM)
- A material in some covers or foams that absorbs heat as it warms up and releases it as it cools, helping the surface feel cool to the touch for a while.
- Pillow top
- An extra layer of padding stitched onto the top of a mattress for a softer, plusher feel. It sits on top like a separate cushion, unlike a Euro top.
- Pocketed coils
- Springs wrapped individually in fabric so each can move on its own. They contour to the body better and transfer less motion than linked (Bonnell) coils. Also called individually wrapped coils.
- Polyfoam
- Standard polyurethane foam. It is used in comfort, transition and base layers and is more responsive and less hugging than memory foam. Quality and lifespan depend heavily on density.
- Pressure relief
- How well a mattress cushions heavy or pointy parts of the body, like the shoulders and hips, to avoid aches and numbness. It matters most for side sleepers.
- Prorated warranty
- A warranty where you pay part of the repair or replacement cost, an amount that usually increases with the age of the mattress. Many “lifetime” warranties are prorated after the first 10 years.
- Responsiveness
- How quickly a mattress springs back when you move. Responsive beds (latex, hybrids) make it easy to change position; slow-response memory foam can feel like it holds you in place.
- Sleep trial
- A period, often 100 to 365 nights, during which you can return a mattress for a refund. Check for minimum nights, return fees and exclusions before buying.
- Spinal alignment
- Keeping your spine in its natural, neutral line while you sleep. A mattress that is too soft lets the hips sink; one that is too firm pushes the shoulders and hips up.
- Support core
- The bottom, structural part of a mattress that holds the comfort layers up. It is usually high-density foam in all-foam beds and a coil unit in hybrids and innersprings.
- Talalay latex
- Latex made with an extra vacuum and freezing step that creates a lighter, more consistent and often softer foam than Dunlop latex. It is commonly used in comfort layers.
- Transition layer
- A layer between the comfort layer and the support core, usually polyfoam. It stops you sinking through to the coils and smooths the change in feel between layers.
- Zoned support
- A design that varies firmness across the mattress, typically firmer under the hips and lower back and softer under the shoulders. Zoning can be built into the coils or the foam.